Im not really good on Mustangs yet, but first I would say get either new dual exhaust (flowmasters, magnaflow etc.) depends on the taste of sound you like, then I believe you can get a cold air intake, or you can get both. If anything I said is wrong, someone correct me. The cool thing is I have the same car and model as you, but its still stock, so im gonna get the Flowmaster 40's. As my first upgrade, then ill get the intake.
UD pulley - easy install ~70 bucks
CAI - Easy Install ~50 bucks on ebay
Exhaust - Shop install ~ can be expensive depending on what you buy, be ready to spend around 300 at a shop for parts and labor.
Alum DS - around 200 bucks.
Not for HP but can increase acceleration.
Gears and T'lock - expensive.
Or, you can go
Ported Upper and lower intakes.
Or if i wanna really get into it, go for ported heads and a cam as well.
Thats really where the power is.
Good thing you used faster instead of fast. But those go hand and hand. Bolt-on's will make you car faster, but not much. To make a noticable difference you have to swap the cam and heads at a minimum. If those items are too expensive for you, you could opt for a split port swap. And since you say you have a 95, I would swap the head gaskets ASAP before they blow. Then I would go with some dual exhaust and you'll be golden until the horsepower virus hits you. I use virus, because there is no cure. You have to feed the need.