Stock gears in the 94-95's are 2.73 OR 3.08. Mine has 2.73. Going from 2.73 to 3.55's will be a nice jump. But don't fear the gear. 3.73's aren't that bad. Our 5th gear is pretty short (.64). You can do the calculations if you wish.
Open your drivers side door, and look in the sticker on the body (where the door meets the body). Under axle code, a Z means you have 3.08. Anything else means 2.73. I think it's an M for 2.73's, but I can't remember.
Get gears. They are the best bang for your buck mod you can do. People usually report increased gas mileage after gear swaps. Do a search on this forum and you will find gas mileage numbers w/ post gear installations.
The stock h-pipe is VERY restrictive. Get a o/r H-pipe or o/r X-pipe. You will not regret it. The cat-back isn't very restrictive. You will not notice much increase in sound from just replacing the cat-back. The cats are the big restriction, and now my car is a blast to drive! (BTW, I am going w/ gears ASAP)
You can get o/r mid-pipes really cheap. Ebay has tons! The cat-backs are around 230 for flowmaster. Since you are on a budget, go w/ a flowmaster c/b, and a MAC o/r X or H. Next should be gears. Then an intake or LT's. It's your decision from there. I have a friend w/ a book full of dyno runs on near stock mustangs. I need to look it up to see the gains. I will post back when I get them.
Scott