4 things we need to know

Budget
Front wheel hub 9mm QR/15QR/20mmTA
Does the frame take tapered forks?
Head tube length (if diving into the used market)


If you go coil & air aka solo air, then you will need a stiffer spring and maybe thicker weight oil. If you go dual air, you will need just thicker oil. You can fine tune the ride feel better w/ dual air. A good shock pump would be something worthy to invest the $30 in.

I'd hunt for a used Manitou Minute, RS REBA, RECON, FOX RL/RLC/FLOAT/TALAS and 32 or 34mm stanchions

Either of these will near top tear, common to find, easy to rebuild and will last a long time. That last phrase makes it worth the extra $$....buy once cry once. And if you have a hardtail, you will rely on that fork ALLOT