Do you have advice on developing proper skill rotations? I usually look on guildjen and metabattle for builds but they rarely have rotations explained. I ask because I just leveled reaper and i have no idea what i’m doing haha
Well, that question largely depends on the kind of content you're looking to get into - depending on whether you're gonna play mostly PvP or WvW, or instead aiming to do endgame, instanced PvE such as Fractals, Strikes and Raids, your builds and rotations will look vastly different.
Since you're talking about rotations, though, I'm gonna assume you're interested in instanced PvE - that is, Strike Missions, Raids or fractals of the mist. Admittedly, Metabattle is not a great ressource for those gamemodes. Instead, you could check out Discretize (for fractals) or Snowcrows (for raids + strikes) and browse their builds - both sites showcase the strongest builds available to each profession, with listed rotations, videos (usually) and additional tips and descriptions, as well as making note of the gear you'll need to get the most out of it.
Unfortunately, Reaper isn't in a very strong position currently, so neither site has a reaper build listed - that's just a fact of the meta, chances are the spec will improve in future balance patches. The flexible nature of GW2s builds does mean that there can be some very drastic variation in damage output between a top-tier build and a more mediocre one. Don't let that discourage you, though! If you really want to play reaper, there is this older build, in the buried archives of snowcrow's site. It's outdated of course, the numbers in the Video won't match up with current gameplay, and there may be more optimal choices to make, but the broad strokes should still work well enough, especially for open world gameplay.
Finally, some more specific advice: Practice!
You can hone your skills in the special forces training area, where you can summon a big golem to fight. It will periodically tell you your damage output too - so you've got a vague idea how well you're doing. If you want to practice for group content, you'll want to set it up right - here is how the raiding community does it. This is a pretty solid introduction to the subject of raids in general!
Some good pointers while practicing: Some of your skills can interrupt others. Your heal skill will always do so, but sometimes weapon- or utility skills can do the same. Learn which ones those are, and try to avoid interrupting your casts. Conversely, try to never delay your casts - unless you specifically want to autoattack, your skills should go off back to back. To that end, skills (provided they aren't the interrupt-ey kind) can be queued - press the button before the prior cast ended and it'll enter the queue. Finally, make sure you're familiar with your traits and your gear. Some builds gain extra damage by attacking from the flank - make sure you're standing to the side or behind any bosses you fight, if that's the case. Some builds have personal buffs they want to maintain, which relies on certain skills they cast. If you know which parts of your build are important, you can focus on those!
For PvP, you can practice in the PvP lobby, and probably find some solid pointers on youtube - plenty of people have shared plenty of builds on there. That said, the word 'Rotation' in PvP means something entirely different - and I'm afraid I'm not super qualified to give advice on that.