Force is one of those effects that works on just about everything. If your PrC has a prequisite number of force spells, take them. Otherwise.. it pays to be diverse. You'll always have your favorite spells, but it pays to be able to handle other situations. I find force to be weak vs crowds though, so another direct damage or two helps.
I just rolled up my own first sorceror and got a lot of help from some folk, heres what i was told
If you can get away with it, take the mininum force effects, and empower spell and rapid metamagic. Then lets say you take magic missile and orb of force. Those two spells just became four with your metamagic feat, one thats always useful to have. Wall of force.. its always useful to have a wall, theres another one and it fits your concept. Take any other spells you want for flavor. Then look at the following:
Protections / enhancements
Crowd control
a reflex save
a fortitude save
a will save.
You dont need too many of each.. even if just one. You already have a single crowd control with your wall of force. I would advise taking web as your second spell, its a useful spell for crowd control, and can even possibly tie up a whole group of enemies.
Will save.. theres lots of these and they come in different flavors, single and multiple. I hear a lot of people saying to take fear or confusion.. they're good spells, but i never could get past the negative of fear: if the enemy runs further into the dungeon/castle/whatever, they may come back with friends. I passed it by. Confusion is also great, but what if that nasty enemy rolls on the 'come beat your brains out' percentage? I also passed it by.. along with fear they're bursts, so it also cant be cast into mellee unless carefully. I took slow: the targets are controllable and the enemy can only take a move or standard action, if i remember right.
I would also advise taking a single target will save spell: a hold spell is a good choice.
Fortitude save is tricky, theres a lot of good options, most single target, take whichever fits your concept, most are game winners on a failed save: baleful polymorph, even blindness or bestow curse can render an enemy ineffective.
Reflex save: These tend to be the most famous spells, usually direct damage. I say skip things like fireball in favor of chain lightning later on, earlier a lightning bolt or fireball is useful to have. if you're dungeon crawling i find lightning bolt more useful: can be carefully cast around your friends in a room and its king of corridor battles.
Also reflex crowd control: web.
Protections / Enhancements.
Some fit into your concept: mage armor is something most mages take. Makes you less squishy and if you have a monk in your party they'll love you for it. Also good for light armored rogues.
invisibility: even when you have improved version, its worth taking.
Haste: i find it better than 3rd level damage spells.. its mass spell now, probably the first thing to cast in combat if you can help it.
Fly: Escape / travel / combat very useful.
Eh.. i'm sure you're not as new to arcane as i was, i wont talk your head off with this any more
As a Sorcerer, you'l be spoilt and stuck for 3rd level spells above all i find. Ive even considered taking 3rd level spells over some higher level ones since theres so many nice 3rd level spells.
Anyway.. take at least one spell for each saving throw and a crowd control spell like web. One wall (probably force for you), and some protections for yourself. You'll eventually be able to pick some more flavor spells. Metamagic lets you diversify the spells you have.