I have the same problem!
I have learned a few and I can get by out on the boat with changing rigs if I take my time. The most important thing I've learned is to be very generous with the line. Rather than trying to tie a knot wasting as little line as possible, make it easy on yourself. Make big loops and leave yourself a long tag end. So far all I have "down" are the Uni (used for tying to termianl tackle, hooks, swivels, etc.) the dropper loop, double surgeons loop, and the alberto knot (for tying mono to braid, not really necessary unless you use braid)
Good luck!