TheSagaContinues

In SAGA your very first character level is extremely important.  What ever class you choose determines how many hitpoints you start out with (18/24/30 before other bonuses), how many trained skills you get to start with, and also what class skill list you are using to select those initial skills.  First level is also the only time you gain ALL of a class's listed starting feats although you may not be able to use some if you haven't met the prereqs for the feat.

After first level what class you take really doesn't matter.  If you select a new base class you get to expand your list of class skills and if you can acquire a new trained skill it can come from any list you've gotten; the first time you take a level in another base class you may also select ONE of that class's starting feats to gain.

A character's BAB is the total BAB of all of the class levels the character has.  A character gets talents and bonus feats as the class tables indicate and these must come from that class's lists; new hp are also determined by the new class's HD.  A character's new general feat they get at 3rd level and every 3 later are determined by character level which is the sum of a character's class levels.  When it comes to Defense scores a character's heroic level is the total number of heroic and PRC level but the "class bonus" used to determine a defense score is only the highest of a character's levels.

I'm not sure if any of that makes sense but now I'll try to show you why/how a "Jedi" starting in different classes would work.  An important design philosophy of SAGA is that names generally don't matter unless some feat/talent/PrC is calling for something specific.  I'll then touch on multiclassing into the various classes.

Jedi start:
This is the easy start as you begin in Jedi and go from there.  This only gets you 2 trained skills with INT 10 and they must come from the Jedi list; Use the Force is very likely to be taken as it is available because of the class's starting feats.  The character also gains Force Sensitive as a starting feat along with Weapon Proficiencies in Simple Weapons and Lightsabers.  As it has a d10 HD the character begins with 30 hitpoints and it has a +1 class bonus to all defense scores and a +1 BAB.  Your talent is selected from any available to the Jedi class and because you are Force Sensitive you may select a talent from the Force Talent trees instead.  With your general feat that you gain at first level you're probably going to take Force Training assuming you selected UtF as a trained skill.

Soldier Start:
You still gain 30 hp but you now get +2 FORT and +1 REF as class bonuses to Defense while still getting the +1 BAB.  You get to select 3 trained skills from the Soldier list.  Starting feats include proficiency in light & medium armors plus simple weapons, pistols, and rifles.  If you want to becomes a "jedi" you almost certainly select Force Sensitive as your 1st-level general feat; this make UtF a class skill starting out so you can select is as a trained skill to fill one of your trained skill slots and it would also allow you to select your talent from one of the Force Talent trees instead of a tree normally available to Soldier.  For the future Jedi a start in Soldier gives you one more trained skill and two armor proficiencies and rifle & pistol proficiencies.  Doing so will almost always mean waiting until you are a 3rd level character before you could pick up your first Force Training feat.

Noble Start:
Starting this way will give you a very different kind of Jedi.  You begin with a +0 BAB which could affect feat selections.  You also only start with 18 hitpoints because of a d6 HD and the Defense bonuses are +1 REF, +2 WILL.  Your starting feats are also very limited with WP (simple, pistol) and Linguist IF you have a high enough INT to use it.  So why start in Noble?  It is because you get SIX trained skills and select them from the Noble's list which is quite different from what a Soldier or Jedi start gets.  You will still be taking Force Sensitive as your 1st-level feat so you can select UtF as one of those 6 skills but after that many "jedi" who start in noble will take the social skills such as Persuasion and perhaps Deception which are unavailable to a Solder or the Jedi class.  In many ways a future Jedi starting in Noble is like starting in Soldier except you're giving up the "strength" aspect of things for a more "mental" advantage.

After first level the world opens up to you.  I generally say almost any character concept can be realized in four levels but sometimes there is a lot of multiclassing going on in those first four levels.  Here is what you typically see when you first multiclass into the previous classes:

Add Jedi 1:  This gets you a starting feat that is usually going to be WP (lightsaber) assuming you took Force Sensitive at first level.  Almost any "Jedi" build that doesn't start in the Jedi class will multiclass into it later to get the lightsaber proficiency.  Sometime a non-Force Sensitive will enter Jedi and they may select either WP (lightsaber) or Force Sensitive if they want to deal with drawbacks that may come from being Force Sensitive.  In any case Jedi is a wonderful class to multiclass into as it has talents that anyone can use (even without UtF or a lightsaber!), a pretty strong list of bonus feats, may add a few valuable skills to a character's list of class skills, and finally its +1 BAB each level and d10 HD mean you aren't weakening a character in those departments.

Add Soldier 1: Another strong multiclass contender as it has a strong list of bonus feats and +1 BAB and d10 HD.  It's talents are maybe a little more focused than what you can find with Jedi but there are still plenty of options.  When multiclassing into Soldier the challenge can be which starting feat to take: WP (rifle) isn't bad if you want a ranged weapon but Armor proficiency (light) or if you already have that (medium) can get you the ability to wear armor.  As you level your heroic level is likely to overcome your armor's REF Defense bonus making the Armored Defense talent needed if you don't want your armor to define you REF Defense; I like a dip into Soldier 1 for many higher level characters as it lets me pick up AP(light) as a starting feat and take Armored Defense as the talent so I can wear light armor and gain all of the non-REF Defense bonuses that it can have.

Add Noble 1:  This isn't something I'd normally do as you have the 3/4 BAB which means your BAB doesn't advance when you first take this class.  Furthermore you usually want Noble for the huge number of trained skills but if you multiclass into it later you don't get more trained skills because of it although it does give you the bigger skill list should you be able to train a skill.  Pretty much the only reason I'd multiclass into Noble is because I'm starting in a tougher class (Jedi or Soldier) and don't want to take the 12 hitpoint loss at 1st-level but I still want access to some of the Noble's talents.

     To expand on what StenvenO said, this system is pretty strong with multi-classing. To illustrate some systems, such as D&D 5e are not very multi-class friendly. With the way it works taking a level of a second class forces you to lose the "capstone" of the base class, granted you would only ever see the capstone at level 20, but the point is even a 1 level dip has permanently locked a powerful character ability. SAGA doesn't have anything like that. With at most 3rd tier talents (there might be 1 or 2 4th tier) 5 levels in a class is enough to get (generally) the best and most powerful things that class offers. If you continue to take levels in the class, cool you get more stuff which the class has, but if those 1 or 2 talents are all you wanted you don't lose out by switching classes. No content becomes "locked" in a saga like system, at least until ~16 level when you simply don't have enough levels left to reach a 3rd tier talent in a new tree. also the PrCs tend to have cool level 1 bonuses as well, such as Jedi Master which gives the serenity trait simply for taking 1 level in the class.
     
     The same applies for base classes as well. You can build a perfectly good, even great, force user sticking only to Jedi and the Force based PrCs. However, even one level dips can be powerful. For instance you wanted a Force Wizard? Let's say you start Jedi, a 1 level dip into noble gets you a boost to WILL and can get you a pretty sweet talent like, "exceptional skill" which makes an d20 roll of 2-7 an 8 for one skill, useful if your using the UtF skill as your primary weapon. Need a bit more survivalibilty against grenades (a Jedi's weakness in this system)? a 1 level dip into Scout gets you +1 REF and the talent Evasion, take half damage form AoE, yep, strait up half damage. So its not that Jedi is a bad class and people simply avoid it, its that the system gives you powerful bonuses for 1-3 level dips into other classes. When ever I build a character concept out I do so to 15 and by that level they normally have levels in 4-6 classes.

Also Fold Space doesn't allow you to teleport yourself (unless you teleport a container/vehicle your in, in which case you would travel with the object), so its not the blinking around the map you might have been imagine. Also the talent waveform is form a Force tradition so you technically need to be a part of that tradition to take that talent (sith are not btw if that what your building), though some GM's simply don't care and let players take talents form any Force Tradition tree so check with your GM about that.

With at most 3rd tier talents (there might be 1 or 2 4th tier) 5 levels in a class is enough to get (generally) the best and most powerful things that class offers.

Actually there are a bunch of 4th tire talents:
Attract Superior Minion
Bodyguard III
Defensive Circle
Fear Me
Full Control
Nowhere to Run
Shield Gauntlet Redirect
Terrify
Uncanny Dodge II

There is even a 5th level talent, Unsavory Reputation, a Crime Lord talent.

Now to get these talents you will generally need to be high level, but there may be some tricks to get one by level 8-10 or so...

As StevenO says it's easier for for a NPC with non-heroic levels to reach deep in a PrC without being of a high CL.

No matter if it is a PC or a NPC, the feat Adaptable Talent lets you choose an extra talent from one of your classes. You get to switch this for one of your other talents once per day or so. I see no hindrance to this being a talent from a PrC, so you could use it for early access for a high tier talent if you have a on essentiell talent from a base class to switch out!