Top tips would be:

Start out on hard (1 skull), not normal difficulty (0 skulls). It’s actually easier. Has to do with the enemies that spawn and the damage they deal. They have more HP, but deal less damage.

When stealthing: be patient. Sometimes it’s better to just lay back and wait for a better moment.

For me personally, not sure how other people do it: I consider heists to be in one of three categories: loud, stealth, and crowd control (kill couple (all) guards, control the crowd, no alarm. Stuff like Bank Heist & Jewelry Store). When you get to the point that you start looking into that, it might also help to make 3 seperate builds: 1 for each.

For the crowd control: always bring a saw. It has infinite ammo as long as you aim in the air, and there’s a skill/talent you need for this, but sound intimidates civilians, causing them to stay on the ground. Causing your saw to indefinitely intimidate them.

I always recommend trying it without mods at first, but as soon as you got some hours in, look into modding at the very least your hud. The extra info helps a lot with everything honestly. superblt.znix.xyz <- you need this one to mod PD2 in general modworkshop.net/mod/25629 <- this is imo the best hud mod out there, but there are others, so you can always try something else ofc

PD2 has become a big game over the years, with a lot of DLC. If stuff gets confusing, just take a breather, do a regular Bank Heist, and recollect yourself :) The non-DLC heists are always a good starting point.

Every map has certain patterns. You can find them on the fandom/wikia, but you’ll learn most as you play them multiple times.

And lastly: DonAcDum :)