Former triathlete here: Unless I ride for less than 15 minutes I'll not get on a bike without proper bike shorts (or longies in winter). Make sure the padding does not have a seam from front to back down the center (outch!). The seams (if any) should have the shapes of the seams on a tennis- or baseball.
Best bike seat depends on the type of bike. You want the back end wide enough so that you sit on your hip bones (men's seats are narrower because their hip bones are closer together). I was lucky enough to have a bunch of cycling friends who let me borrow their seat for a 30 mile or so ride until I found one that worked for me (actually a men's model but a fairly wide one).