PKjump isn't hard... for me...
Fair isn't particularly good for approaching.... it is good for DEFENSIVE approaching. (You need to retreat fair in order for it to do what you want... or hit with it and then go forth...)
I recommend either RAR FH bair, RAR Nair, RAR FH Nair, Nair, RAR bair, or just FH PKfire.
RAR bair, because it can hit taller opponents in the face on the way up and I like bair.... It also catches people offguard and allows for a falling nair/uair/airdodge to whatever.... I need to check though, because I haven't used this one in a long time... like srsly.
RAR Nair b/c you get uair as an option... uair has insane backward range... you'd be surprised how far it hits.
RAR FH Nair, because you can bair and uair going down, and if you really need to you can maneuver for a fair landing and nair if your opponent has some quicker stuff.
RAR bair is my favorite. You have to space it perfectly though. You get uair and nair to end it with, but I recommend using DJ after it... If you are super pro, you can reverse pkjump from that SH RAR bair... It requires so much precise timing.... not worth the risk.
FH PKfire is just a great move for any situation. Done right, you get a uair on landing and it can catch people offguard very well.
Something I found with FH PKfire.... I don't know how to execute it perfectly every time, but I've been able to make it so that (I believe) I begin movement like a RAR, then PKfire forwards (direction ness isn't facing), and it wavebounces... It's so weird... It gets you like an extra couple inches of movement away from your opponent for some safety, and you can fake out opponents and make more precise PKfires... This requires usage of L button as jump.... Regular, you may not be able to pull out pkfire quick enough and can undergo some landing lag.
I just say anything FH can be used as a successful approach, except maybe dair... FH dair is only if you expect your opponent to think you are going downwards.