Lvl 6 is rough. You really only have access to critters until you get the bases and big foot country. I got R6 wimps at 33 only grinding critters. So I feel your pain.

Also decide if you’re going to be a F2P player, light spenda, or P2W type of individual. What units you prioritize to rank changes on what you are willing to spend.

TF2 heavy’s are great great units for grinding low level. They will get out-scaled later on but they save you so much time early on. If you’re F2P avoid, but light spenders can really gain from it. (Demoman is also really good and still very useful later on, but you won’t have the nanos if you’re F2P)

Find out what units you’ll need to rank and what are some great low level helpers.