Do you spend everything you have on low level items?
I will almost always do this. You get 80% of your money back when you resell your items, so it's worth it.
Save it for better gear a little later?
I don't generally do this. Never save for an artifact at level 1. It has n00b written all over it. Generally, the lower cost items actually have a better benefit/cost ratio. Usually, you should get better items only after you run out of slots.
Buy your favorite favor item?
When I use a build that relies on teleporting, I'll usually get the amulet of teleportation. Otherwise, I try to wait before I buy my favor item. It's usually a good idea to see what strategies your opponent is using before buying a favor item.