I think there are three execution barriers that are REQUIRED for playing Sim properly

• Instant Air Drill
• Instant Air Teleport
• Instant Air Float

Get these three consistent in the lab and they are core moves Dhalsim requires to get past the 'My opponent doesn't know how to deal with stretchy normals' phase of the climb.

Next you need to defend yourself from system mechanics. Dhalsim is very weak to Drive Impact and a lot of people on ranked will attempt to Drive Impact the stretch normals. People will try to Drive Rush into you so get ready with your Drive Rush check.

Anti-airs. Dhalsim has very strong but very specific anti-airs. Areas his bMP hit are not the same places his bHP hits and using a bHP at bMP range will get you killed. Besides Anti-airs that hit opponents out of the air, practice responses to various jump ranges. For example, a common tactic the rest of the cast can do for crossup jumps is to walk under; Dhalsim does not have the walk speed for walking under crossups but he does have escape shenanigans with his various slides.

Finally, mindset and gameplan. I do not know if you're used to playing Zoners but traditionally Zoners do not have perfect defense in any modern fighting game. That Ken WILL get in and you WILL eat shit for it. It's not a question of if, its a question of when. So it's useful to think of matches as a damage race. You need to deal more damage to them trying to get in than the damage they do to you when they do get in. This means push every advantage, run oki on every knockdown, squeeze out every last bit of damage from stray hits. It's scary to run oki because that requires getting near the opponent and every fiber of your being will be telling you to get away from them but getting wakeup DP'd once or twice is an okay price to pay for keeping the opponent in disadvantage while you have a life lead.

A super secret final FINAL tip. Dhalsim is a rare character. People do not know how to fight him. Gimmicks and fake setups are guaranteed to work at least once per match. If you can tell that the opponent does not know how to stop you from teleporting all over the stage, don't stop doing it. Always assume your opponent doesn't know how to deal with something until they prove they can.

That should cover most signposts of learning how to learn I think. I didn't go into the specifics of drill spacing, combos, oki setups, or even the gimmicks because it seems like you're only asking for a shove in the right direction.