I want to modify/upgrade my Elantra

I have had my Hyundai for 8 years now. It's paid off and I have had a company car for about 4years, right after I paid mine off. So i have not done much with it. I want to upgrade the performance (get more horsepower) of my 99 elantra without going too crazy. I pretty much want to upgrade things I can do myself. I have been looking around a little and was thinking of adding a supercharger or turbo, a cold air intake manifold, maybe a chip and changing the muffler. Has anyone done any of these things and if so, can you tell me about your car's reaction to the modifications? is there anything you can suggest looking at or doing?