Really need to start level Combat but it feels so slow 
#Any tips for level up Combat?
supple canyon
lone breach
Agreed! My other ones are either level 10 or almost to level 10 except my combat... i think just grinding and killing monsters is the only way to level your combat unfortunately
worthy anchor
Killing monsters isn't the only way, if you craft traps they give exp on activation, so if you build the spring traps and walk monsters into them they get exp, and can trigger multiple traps at once, I got 1k when doing it to one mob per day or 3k+ when doing it against an advanced slime and having it spawn some smaller slimes aswell (only need like 4-5 slimes but they do get caught in walls at times) the spring trap costs 5 wood and 2 of any ore per craft and provides 2 traps per craft, I also recommend getting the traps last 30% longer perk helps keep them around longer (not about craft efficiency more just less replacing them for when a good bounced enemy goes through them all)
and I could be wrong but I think the decoy craft has a slightly larger aggro size than the player so that might also help, but I did it without. Took me 6 ingame days to get from level 6 combat to 10
The other option if you don't want to spend resources/money on traps is to farm the slime spawns from advanced slimes, I saw someone say they got around 600-800 exp per day from it. which is pretty good, and a really good farm for slime goop.