Prestige Class General Question - Optimization

[ReliantLion]

I am making an Arcane Trickster for my friend's campaign.
The levels I will be taking are:
1-2 Rogue
3-4 Sorcerer
5 Rogue
6-8 Sorcerer

At level 9 I meet the requirements to do Arcane Trickster. So my question is this, do I take Sorcerer to level 10, then do AT 11-20? Or should I do 9-18 as AT, and finish off 19-20 as sorcerer?

Is there a general "Prestige classes should be done this way...to optimize"?

[Wasum]

you should get into AT earlier. You dont want 5 levels of rogue as it kills your spell progression.
Actually rogue1/assassine1 would be best, but guess being evil is not what you want.

[ryric]

Honestly arcane trickster, done the "normal" way, by multiclassing rogue with sorcerer or wizard, is not really an "optimized" choice already by most standards. That's not to say it's not fun - I've had a blast playing an arcane trickster - but it's never going to be the party superstar.

That having been said, if your plan is rogue/sorcerer/AT, here's what I'd do:

Start sorcerer. Go all the way to 4 to get your level 2 spells.
Now take 3 levels of rogue. See, the problem is that a rogue/sorcerer is less effective than either a rogue or a sorcerer who just stayed with what they do. Those levels where you're building the other class can be painful. Going rogue second minimizes those levels(3 instead of 4) and at least you have your 4 sorcerer levels to fall back upon. 7th level will be the most painful.
Go into your prestige class right away. Multiclassing with a spellcaster is harsh, and the PrC is desigend to ameliorate some of that. Delaying it is really just not a good idea. Plus you get some decent abilities from arcane trickster that you want ASAP.

I would not recommend splitting up your multiclassing as you describe as that prolongs the "pain" levels. I also don't see why you need 5 levels of sorcerer in your proposed plan.

[Gregory Connolly]

Generally from an optimization perspective Rogue 3/ Wizard 1/ Arcane Trickster 10/ Wizard 6 is how arcane tricksters work out. You can sub Ninja, Vivisectionist and Witch without changing the math but Sorcerer doesn't get 9th level spells. For a Sorcerer to be an optimal Arcane Trickster it goes Rogue 1/ Sorcerer 4/ Assassin 1/ Arcane Trickster 10/ Sorcerer 4.

If you aren't going to retrain, I would say take Arcane Trickster now, you already lost 3 levels of caster progression. If you are just making the character now take Arcane Trickster from levels 5 to 14, the class isn't really that good compared to others like Eldritch Knight and Mystic Theurge so taking it late is likely to result in wishing you had played something more capable.

[ReliantLion]

I guess I should have been more clear about the levels I intend to use. He is starting at level 4 and will have 2 rogue levels and 2 sorcerer levels. At level 5, I will take rogue again, before doing sorcerer until I can do AT. He has the magical knack trait, so only loses 1 level of caster for most purposes.

I want it optimized so as not to just totally not work. We have a large party, so we have more room for custom characters.

Thanks for the advice about taking AT asap, which is what I was really wondering.

Besides the mechanics, the backstory for my character implies rogue/sorcerer, growing into AT. Assassin wouldn't work thematically, unfortunately.

[Gregory Connolly]

Well, the clarification helps. If you are playing a sorcerer/ rogue I would start it as Rogue 3/ Sorcerer 1. You gain basically nothing at all from level 2 of sorcerer compared to level 3 of rogue. If you don't want early access from wizard you can still get it with a racial SLA and take your 5th level in AT. The idea here is to only take 1 level of sorcerer before AT because you get so much more from AT than from sorcerer.

[LuniasM]

If you're optimizing, the easiest way in is via Early Entry using a 2nd-level arcane Spell-Like Ability. Certain races can pull this off using alternate racial traits - Half-Elves, Drow, Tieflings, Aasimars, Duergar, and Svirfneblin all qualify for early-entry. This allows you to get in as early as Level 5. Three levels of Rogue, Ninja, or Vivisectionist Alchemist give you the Sneak Attack and one level in any arcane spellcasting class gives you Mage Hand.

If Early Entry isn't available, your next best bet is to minimize Rogue levels by prestige classing. Due to the way sneak attack is worded, one level of Rogue or Ninja and one level of either Assassin or Sleepless Detective at 6th level will give you 2d6 sneak attack. I personally recommend Sleepless Detective as it gives you Detect Magic at-will and can give you a bonus to certain skills. If you don't mind being Evil, Assassins can be good as well. This allows you to get into Arcane Trickster as early as Level 7. *Disclaimer: This method is technically RAW but don't be surprised if your GM bans it.*

Examples:

Early Entry Method (Enters at 5th): Half-elf Rogue 3 / Sorcerer 1 / Arcane Trickster 1

Prestige Sneak Attack Method (Enters at 7th): Human Rogue 1 / Sorcerer 4 / Sleepless Detective 1 / Arcane Trickster 1

[KainPen]

a Teifling and Asasmar can pull off early access as Gregory pointed out. there are actual several subsets of Teiflings that can be played so you don't take a hit to cha but to something else instead. Also This allows you to gain a bonus to cha if you take abyssal or infernal bloodlines. I suggest taking Abyssal via eldritch heritage feats, For eldrich heritage chain you get +6 to str so if someone does get in your face you can do some damage without spells are use SA a little more effectively and extra creature whenever you summon a fiendish monster. Along with resistance and bonus to saves vs. poison. Since the character will have low fort save. Also magical knack as a back ground trait to also make up for rogue levels few of those rogue levels.
Robe of arcane heritage will increase bloodline powers and grant early access to some of them. (not ones granted by feat listed above) making up for a little bit of multi classing you are doing.

total
3 Rogue
7 Sorc
10 AT

CL total will be 19 due to magical knack
Spell known will still be 17 but you will extra bonus spell and DC will be higher if you take infernal or abyssal bloodline
With the eldritch heritage feat chain you will function at total character level -2 until you get the last one then it will be treated as total character level for the blood line power (there is debate if the robe of arcane heritage increases this to +2 or +4 more level for non sorc but you are one should work. )
And the base bloodline you pick will function as level 11 with robe and you will have access to the level 9 powers because of the robe.

It not uber but it does make up for some of those missing levels.

[Saigo Takamori]

Fast question: do you plan using essentially your spell, or to play your character more like a rogue? In that case, why not take the Archeologist/ Rogue way? You will enter the PrC as fast as the Sorcerer, but you will get far more competence and be, I think, more viable for the time before de PrC.