I'm 17 as well, and I've replaced all stereo components in my WJ
I have yet to add a sub, but I had 2 in my old WJ.
Since you have a wrangler, space is at a minimum. If you want your speakers to sound great, I'd suggest getting a 5 ch amplifier. This will run all 4 speakers plus a sub. It also makes it easy to run RCA's to your amp from your head unit. If you don't want to do that, a mono amp will be just fine. The 5ch is a bit more expensive, but it'll make your speakers sound great.
I'd also suggest getting a JL Audio sub instead of a Pioneer. An 8" sub is weak in some people's minds, but I've read reviews of a JL Audio 8" sub that sounded like 2 10's. Trust me, you're gonna want that JL when your friends are blown away and ask about your subs, and you tell them it's one 8. I've never heard them personally, but I've heard only good things about JL Audio.
On my WJ there is a factory grommet on the driver's side that I ran my 4 AWG wire through to my amp. The power wire is laying across the engine bay, but it has caused 0 problems for me and for my last Jeep. Idk where the grommet is on your TJ, but it's easiest to run it through the factory grommet in the firewall, or you can drill a new hole if you wish.
As far as equalizer settings go, here is what I do: I set the equalizer settings to flat (+/- 0 on all Hz settings) and listen to a few songs. If I feel like a certain Hz setting is lacking in the songs, I'll bump it up a few decibels. Nothing too extreme, just make it sound good in your ears.
I've drilled holes under my rear seat to mount my power distribution block, and it scared me at first (drilling holes in my fresh WJ
) but I got through it. The center console may have instructions for drilling new holes, but if not, just line up the holes when you get your new sub and drill away.
Hope I could be of some help! Good luck!