Try to stay away from all the $10-$50 "accessories" like shakers, tank bangers, octo holders. These never seem to work as well as I though they would standing in the dive shop. Another rule of thumb I try to follow is making sure all your gear is versatile, along the lines of a BFK - the BFK is like 6 tools in one. A trilobite is a good cutting tool, but really only for mono or other thin line - save your money and buy a BFK!
For big purchases like regs or BCD, buy the best you can afford - for example, save a few more dollars for a cold water rated reg, if there is ever a chance you'll dive cold water.
I'd also caution against buying "travel specific" gear - IMO I don't mind lugging a few extra pounds through an airport 1x or 2x a year. The super lightweight versions just aren't as durable.