I'm looking between 1,500 to 3,000.
In Australia that would get you something unroadworthy or only suitable for parts.
No idea what $3k would get you in Florida. Maybe that'd be more than enough to get you a good 'un.
Honestly, milage is probably less of a concern than getting a good one. I wouldn't buy one over 180k miles personally, but I know examples of NAs in the club in Melbourne that are still running sweetly at track days on 250k miles, because they're looked after. And I'd rather by a good one with 180k than a dog with 120k.
If you're after an NA, beware rust on the inside of the front fenders, terminal hydraulic lifter rattle, serious oil leaks, the plastic on the radiator perishing, grinding gearboxes and dodgy diffs. Also, look up the short nose crank problem and make sure you understand what it means and how to identify them. It's complicated so I won't go into the whole thing, but the early 1.6 engines can fail very easily and catastrophically if some things are done wrong to them.
But apart from that the engines are fundamentally very strong, and will probably go forever if maintained well. Also, beware suspension on 25 year old cars, if the shock absorbers haven't been changed they'll almost certainly need to be. Will improve the driving experience immensely.
NBs are mechanically almost identical, so a lot of the same things apply.
Miata.net has some great guides to buying, I recommend having a read.
If you have specific questions I can do my best to answer. I do own a white '90 NA, which is kind of giving up the ghost at the moment. The hydraulic lifter rattle has become very strong recently despite chemical additives, I had the radiator blow it's top, and the gearbox is starting to grind more. I have in the past done a fair bit of work on suspension and bracing the car, and it's still really sweet to drive, it's just the mechanical bits are kind of giving up. I'm at ~150k miles, but it's on it's second motor with unknown kilometers (someone swapped in a big nose before I bought it).
I'm trying to organise daily transport for myself so that I can take it off the road for the winter and fix it up, because I'd rather not sell someone a dog.