I have a 95 3.8l camaro. The steering wheel shakes back and forth. It's the worst between 80 and 120 kmh and when im braking. I feel a little vibrations in the gas peddle too! Is this the drive shaft or suspension issues? any help is greatly appreciated!

could be,
something simple like a worn tires....something not so simple like a tie rod, ball joint and such.

should i get new tires and alignment and go from there?

I had that same problem and it ended up being one of the u-joint outside snao rings came out and the u-joint cup backed out to let the drive shaft vibrate.

If you need new tires, yes that would be a great place to start....I would borrow a friends tires...
IMHO, you can put the car on jacks and check for wheel bearing end play= grab the wheel and gently try to move around on the hub while staying away from the steering axis. Grab the driveshaft and shake it..BUT, since you specified the steering wheel most likely its up front....
During alignment they may catch your prob who knows..

ok, first the 80-120kph, which would be 50-75 mph. I would go get my tires balanced first. The shake more then likely comes from out of blanance or out of round tires if it happens through the steering wheel. Now the shake you talk about when you apply brakes makes me think to much runout(warped brake rotors) on your brake rotors, which you will also feel through the steering will and sometimes the brake pedal. As for the shake through the gas pedal...no idea, sorry.

I would go to a tire shop and get all four tires balanaced and have your brakes inspected while the tires are off. Most places will check out your front end while they have it up in the air, that how they make money. Alignment on its own is very unlikely to fix a vibration. My shop does a couple hundred alignments a month and I tell the customers that before I do the alignment.