One tool that gets neglected is a plumb bob only a few quid and great bit of kit for getting a plumb line in awkward spots, and a chalk line to go with it (handy when the lasers batts have died:lol
I recon starting out you should spend £50 or so on a few bottles of good cleaning products heavy and light duty lithofin, hg etc
One of the things I always carry... As im starting out alone I have enquires to alot of Cleans,Re-grouts & Repairs