Frontside boardslide the end of a ledge is a good rudimentary one to have under the belt already, doing longer ones on ledges and taking them to rails is essentially the same thing but mustering the balls to actually get onto the obstacle at a scarier moment, I'd say progressively learning to do longer and longer ones by popping into it earlier (still dismounting at the end, it doesn't matter yet) could be good practice. Mid ledge dismount is a bit awkward at first and takes finesse but it's essentially a weird ollie out mixed with a front rock type of motion, so relatively accessible but maybe best kept for last. Generally speaking, starting slow and low till you figure how to lock in consistently, and then working your way up (key point, because some people find it tempting to forget to work their way up) is how it works for most ledge tricks at first.
You should start learning ollieing into 50-50's, if you can ollie up curbs it's essentially the same thing just with more specific guiding and aiming (front foot leads the ollie, shoulders/hips help align it over the edge). Start on something low so you don't really risk much when fucking up. Frontside is easier to some (me included) but working on backside simultaneously could be a good idea so you don't develop a preference that will hinder your skating later. Then 5-0 is essentially the same thing except you stay over your back leg and balance it like a manual. Nosegrinds are harder and should probably come later, but you could always toy around with how to grind them too. Anyway once you start getting 50-50's, it's super fun to start trying to 50-50 literally everything you know you can already ollie up, incrementally.
You could do noseslides but honestly I find that the feel of most backside noseslides sucks, maybe it's PTSD from doing too many of them as a kid but it's one of those tricks most people learn super early on so they struggle with it and finally, even when they can do it it's still a frustrating trick. But they should be accessible too and slappy is fun and can be taken to taller things. Frontside noseslide though is a treat and is worth learning ollieing into (which I view as as basic as a front board tap), you can do that by coming at an angle at first and then slowly dwindling said angle as you get comfortable. Backside noseslide to fakies are essentially frontside 180's with a break halfway through the trip where you just sit on it.
Crooked grinds I also have a love/hate relationship with (I much prefer them switch) but they're also easy, as long as you don't think of them as weird noseslides and instead, more as weird nosegrinds, to force yourself to really get your truck on there and put all your weight on it.
Your progression should essentially be, first learn the trick on a ledge, then a rail, then take it to handrails, at least for most tricks and if you're trying to take a safe route.