Minggstraight airs with grabs(safety is easiest)
Also, another one that I find easy is a critical. I learned a safety first (lol "safety first"), and I learned a critical next. I learned it faster than the safety and it's still easier for me to do a critical than a safety. They're both good starter ones though.
Anyways, yeah. People progress differently. I've been skiing for about half a season so the best thing I could do is list off my progression.
In the half season I got, I learned how to ski down regular trails first. Then I went for the more advanced ones, and THEN I got into park. First, I got comfortable with the jumps, and then I learned a safety and a critical. I can slide boxes, 50/50 boxes, and land switch out of boxes, but I still have trouble with rails. On the last day of the season I did a 360.
This summer I've been using a trampoline/diving board whenever I can and I've learned: Frontflip (with various grabs), backflip, lincoln (with various grabs), Misty 5, Misty 7, double frontflip, 1 1/2 backflip dive thing, 7s, and 9s.
My advice would be to use tramps and boards as much as you can right now.