I'm sure there is already a topic for this but it's probably old and I feel I need a little revival with my Fallout games.

So!

I've played through FNV a few times, about 2 full and now working on a third, and I was wondering what more I can do in this game? I know I haven't done EVERYTHING because I haven't even touched Ceaser's Legion's storyline. My first playthrough was mostly using the guns, speech, and barter skills and pretty balanced SPECIAL stats. My second I started to lean towards melee skills, sneak, and science because ya know... Science is always real sneaky like, right? haha but I went to almost every location, did (I think) every side quest not involved in a faction and finished every NCR quest. Did the main story along with the BoS stuff and Boomers. I'm pretty sure I liberated Black Mountain but I'm gonna do it again because I don't remember any part of it I basically exhausted all the things I can do playing the character I wanted to make.

Is there anything I should do that I haven't tried yet? Or anything as a generality that I should try anyways?

I haven't played through the Kings or Ceaser's Legion, so should I do those? Is it worth it?

Are there any places I should check out for looting reasons or because of how spectacular it is?

Is there any general builds I should try?

Just stuff like that, any suggestions?

Also: how do I get power armour? I've played this game upwards of 75 hours and I still don't know how to get Power Armour training

To get power armor training, either:

Welp... Back out into the Wasted I go, I'm gonna get me some power armour training!

The Kings are a fun set of quests. The Legion, well you have to figure out if you want to go that route.

As for reasons to play the game when the quests are done, Collecting.

If your on the PC, get the Underwater Hideout and try to fill the weapon display walls.

Try Unarmed and Melee, get the T51-b, buff Endurance and Luck, get all DT perks and crit perks... Then start walking around and rip heads off!

Why would you not do a Caesar's Legion playthrough? If you do it intelligently and covertly (i.e. don't just start openly annihilating NCR camps and then wonder why your playthrough has devolved into a tedious slugfest) its probably the most fun of the main quest paths.

When the game gave me the choice to choose my side I just didn't find the appeal in going to Caesar's Legion. I don't know why, I try to keep my Fallout games up for spontaneous choice-making and I guess that just led me to stray off from Caesar's path. I'll definitely try his quest line out though, I've heard a lot of good things about it. It's just, to me, he isn't that great at face value.

Collecting could be a lot of fun, especially with the Gun Runner's Arsenal. It adds an enormous amount of unique weapons to collect. I would play my PC version of the game (with the underwater hideout) but my computer doesn't handle the game very well even on Low settings, which is weird because it puts it on high by default

No I agree the entire concept of Caesar's Legion in-universe is absolutely unappealing and terrible but its an entertaining gameplay path and there's no reason not to try it at least once.