I wouldn't spend money on glass negative carriers yet. They really are not necessary unless you go up to 5x7 or 8x10. If the problem is negative pop, it can be alleviated by turning on the lamp and letting the negative warm up . Once in a while you will get a neg that seems finicky in this regard but it can still be exposed satisfactorily. I've only had one 4x5 negative that gives me this problem. It ahouldn't ever be a problem with 35mm.

Make sure your condensor setting is right for the format. You can actually "focus" the condesor by turning on the lamp, no negative or negative carrier in place and "focus" the projected light on the baseboard by moving the condensor adjustment. Try it, you'll see how it works.