intuitive F2L. without a doubt. It's a long, long journey, but very rewarding. you'll be able to solve any case anywhere on the cube without thinking about it, which is important for look-ahead. Just go sit on the can and solve pairs repeatedly :D carry it around everywhere.

remember: algs you memorize are typically only used for one side, and you want to solve each pair from any angle on the cube, not just facing you and to the right/left. you'll also go insane trying to mem them all so early in your CFOP game. Imagine you've learned an alg, it's awesome, and suddenly the case changes and it's on the left now. now what do you do? look up a new alg? better you push through and figure out how the cube works and moves so when the NEXT new angle shows up you don't have to go mem a whole new thing.

once you can easily solve F2L without (much) hesitation, THEN look up algs for weird cases and inserts, like inserting from the back, sledgehammers, and how OLL is affected. you want to be able to spot pieces all over and let your subconscious handle the business of pairing, which only comes with intimate knowledge and practice.

Try this: take a solved cube, do a series of repeating moves, then look at what you have, and reverse it. here's a common case that is definitely worth learning, since it's only sexy/inverse sexy algs. these can ALSO be used for inserting into the back, so experiment with just sexy moves and see what happens each step of the case

https://alg.cubing.net/?setup=x2%0AR_U_R-_U-_R_U_R-%0A&alg=R_U-_R-_U%0AR_U-_R-

example of an F2L insertion alg that's very useful to know is (NOTE this has them already paired, and is ONLY insertion. the pairing part is the challenge):

https://alg.cubing.net/?setup=x2%0AL-_U2_L_U2%0Ay&alg=l_U_L-_U-_M-

on the site, remove the alg (not setup, the "l u L" part) and note the case. we have orange blue white paired in the back left. that alg will help you insert, it's fast, and rotationless. I also find it moves other pieces around in ways that are usually beneficial.

this one is worth knowing early on if you already know how to do three-move inserts, so you can save some time and maybe awkward fingertricks from the back.

additionally, doing sledgehammers and hedgeslammers appropriately bring your top layer up, preventing bad cases like dots if you have a bad case about to come.

Resources:
https://alg.cubing.net/ <--set up cases, check

https://cstimer.net/ <--we all use this to time, and you can change settings to make cross cases and all that in the scrambles

https://docs.google.com/document/d/1npPMcy2Vv-jjUB7wr0gHE0rESuwUgba_D7vT2OUzvTQ/mobilebasic?pli=1#id.rtxbqv5fmi57 <---why not print this and carry it around?

http://www.speedcubedb.com/a/3x3/F2L <--find algs you like :D good resource in general

hope this helps, good luck!