For the longest time I only had a long, 8''x24'' ish ruler. Long enough to do straight rotary cuts across a yardage of fabric. If it has angle markings on it, you don't really need any of the other rulers. But, getting more gadgets is always fun, and can help a lot. I bought a square ruler to help with squaring up my HST's and blocks, and found that things went so much more smoothly. I think basic rulers are always a good idea, and the specialty ones saved for if you have money to splurge.
