i self taught myself about 6 months from don't know how to swim to know how to swim.

part of the drills includes
1. review the recording myself swimming
2. watch youtube and understand what style you want to achieve (for me was to join triathlon 1.5km swim and swimathon 6km , so any style will work however backstroke and freestyle was the most efficient.
3. i swim 3-4 times a week on a 25 or 50m pool from beginning 1lap to 100laps. build up your distance at your comfortable pace.
4. have a few open water swimming to get use to the sea water.
5. as for gears a decathlon basic waterproof watch will to do your timing, advance you can go for gps based watch. ( i use a zeblaze swim and amazfit trex interchangeably) , googles is very important and pool ones and sea ones are different from a lenses perspective, and accustom to wear head cap and swim wear including tops because the sun will burn you.
6. from a technique, technique is priority before stamina, i use a swimming snorkel, a kick/pull board to fine tune technique. similarly like gym, leg day, strokes day, full body, core too.

Hope this helps whomever reading.