^^Agreed^^ Mods are only worthwhile if you do them to help your bike look or perform better than stock. Aftermarket parts can get expensive quick, so don't get too carried away at first!

I would go ahead and get some better tires. The stock balloon tires on a Blaster are worthless if you plan on doing anything more than just cruising around. Maxxis, Shredder, and ITP all have plenty to offer.
As far as the engine is concerned, a new exhaust is the one sure-fire mod that you will NOT regret. A good pipe will wake up that 195cc mill in a hurry. There at least 10 major brands of pipes available for the Blaster engine. I'm not gonna start a mulit-page debate over brand names here, but I will say that a "left-bend" expansion chamber works best on stock-bore/stock-stroke Blastys. I have a Toomey exhaust on my 2005, and it delivers. Bill's, Shearer, and a few other's also work well. I'd stay away from FMF and DG.
If you decide to upgrade your exhaust, go for it! I:I BUT, don't forget to re-jet the carburetor to compensate for the resulting improved airflow. That's what I like about Toomey Racing. They offer a complete exhaust kit, with the pipes, all hardware, new jets, and UNI air filter in one easy-to-install package.
What else can you do to a stock Blaster without breaking the bank? (And by that, I mean mods for under $ 500.00). Install a K&N or Uni air filter, and re-jet. Get rid of the oil injection. Equip your engine with V-Force 3 reeds. Install a hydraulic rear brake kit if you own a pre-2003 Blasty. Try a wider rear axle for better stability. (G-Force makes a good product at a reasonable price.) Wider front A-arms help a lot with stability, too. The TORS system can be removed from the bike. You might also want to upgrade your shocks, as the stock ones are stupidly soft. Try a set of Works shocks. I could go on and on, but these mods are my faves. Some of what I've described is pending for MY machine...