skipping practice league has its own pros

1. the game speed on practice league is set on "normal", while in ladder, the speed is "faster"

2. the maps in practice league is modified compared to the "normal" maps available

just lose a couple of match during laddering, watch replays, ask for advise in forums, and play-play-play, and you will improve

unless

you are very particular about your "win-lose" percentage, then again, you can always go play custom games, and ladder once you are confident enough