FM is not a bad idea, but before you call, think about three things; your budget, what you intend to do with your miata (daily driving, street driving with perhaps an occasional autocross, maybe a track day once in a while, driving school, or a garage queen that only sees the road once a month, etc.) and -be honest with yourself here- the level of your driving ability.
Don't be self conscious about an honest appraisal of your driving ability; it's a continuous curve, and you'll always be improving. Build the car to suit you and your abilities, and you'll be happiest with it long term.
I drive my latest, a '92 two/three times a week, and (now) autocross it infrequently. . .maybe three times a year. I suggest:
First, take care of the brakes. Install a set of Hawk HPS pads (or an equivalent that you like) and stainless lines. I wouldn't bother with switching to '94-'97 (bigger brakes,) since the stock set up with the aforementioned upgrades is good enough for Spec Miata; they'll work for hard street use, autocrossing, an occasional short track day. If you take it to a driving school, get some race pads, depending on the track time involved.
Install front and rear control arm braces. If you're a cheap bastard like me, make your own out of 1" tubing. (Google it/check miata.net)
Next, if you want bigger rims/tires, get those. I wouldn't go larger than 15". When I bought my first miata,l a '96, it had 17s and very low profile tires (35s) on it because the PO thought they looked cool. It rode pretty hard, but had excellent turn in feel, and rubbed the fender wells a little. Tires were $$$ to replace; they were easily damaged when hitting railroad crossings/potholes. My wife killed two in one week. Ah. . .blissful matrimony. . .
The bigger the rim, the lower profile tires you will have to go with to make them fit within the wheel wells. Low profile tires equal stiffer side walls, which equals crisper feel, but less compliance in bumps and most importantly, you'll get less warning when they're about to break loose should you choose to drive spiritedly. 15s with some good 50 series sticky tires are the best compromise in my opinion, but go to a local miata club gathering and try to ride with people that have different setups before you choose.
What made a BIG difference for my car was a set of urethane suspension and differential bushings. WELL worth the $$$ (about $350) and trouble to install them.
Consider a Flying Miata butterfly brace. They can really make a difference in terms of chassis rigidity and therefore the effectiveness of your suspension. Keep in mind that you have to drill holes in your car to install one. They also may not be legal for the autocross class you might want to run in, so check rules first.
Now, this is where you driving ability really starts to factor in:
If you want to have your car corner flatter and faster, get a Racing Beat 7/8" front antiroll bar, and a 5/8" rear bar. Consider also getting a Racing Beat Sway Bar kit. Keep in mind, like the tire changes, your car will corner flatter, and therefore faster, but you'll get less warning when the rear end starts to come loose. If you want better corner carving, and can handle a car that oversteers more quickly, but at a greater limit and with less warning than the stock set up, then go for it.
If you can handle a stiffer ride, consider getting stiffer springs. For me, 30% stiffer fronts and 20% stiffer rears are still reasonably comfortable for street use. FM and Racing Beat both make springs that fit these criteria.
Get KYB (I like GR2s) or Koni shocks as well.
As far a intakes, headers, etc., you're going to get fairly modest gains, about 10% max. I put a Jackson Racing stainless exhaust, about $500, their high flow catatlytic convertor, about $250, one of their 4-2-1 headers (can't remember price,) their cold air intake $300, and some high end plug wires, and advanced the timing a bit on my '92 and saw a gain of about 10 hp if I remember correctly. The difference in acceleration was noticeable, but given the amoun of money involved, I feel a greater impact was made by the suspension upgrades I've done. Also, with the Jackson Racing exhaust, the exhaust note was noticably louder, but still liveable.
Best of luck with your car,
Steve450