rosin core solder

Try get lead free solder if you can. WBT silver solder is what I use.

The flux I use is called honey flux over here. Not sure what its official name is, but it looks and runs very much like honey. It's for soldering to alu, but makes other jobs very easy too (nickle, tin, stainless, etc.).

Also, make sure you've got solder tips for all types of jobs you'll be doing. Thick tips for heavy gauge wire and SubC cell terminals. Thinner tips for servo leads, antenna cable, electronic circuits, etc.