I have had two 3D printers, a Robo 3D Cartesian and currently an FLsun Delta. Learn everything you can about the mainboard and the software options for it, then say if it's Marlin learn everything you can about marlin and which commands your mainboard supports. Bed leveling and proper Z-offset are the first two things to master. Don't go berserk with printing "upgrades" for the machine right away. Learn it first as I've found about half of the "upgrades" are more of an excuse to print something because you've run out of ideas and don't really help you print better. There should be a FB group or hopefully a forum for your particular machine, these will be the most helpful places to seek advice specific to it. There should also be YouTube videos for repair and maintenance. As far as filament goes Make sure you're buying the right size for your printer. Hatchbox Wood PLA filament and Proto-Pasta PLA are two of my favorite PLAs, eSun & Amazon brand are decent. PETG is a matter of what's on sale and what you plan on doing with it, some blends are brittle and don't take impact or flex well like a PETG should. 3D Solutech, Tianse and YOYI brands always work well for me. Flexible filaments like TPU/TPE work best if you print slower. If you want to do ABS or Nylons you will need an enclosure or tent around the printer for best results, they tend to warp. Most of all in the beginning you will need Patience. A nozzle clog 18 hours into a 35 hour print is a mofo, but it happens, you change your nozzle or needle it out start over and move on. The only brand of filament I've consistently had problems with is Inland.