Detonate Trap is very useful to get rid of Boss Traps and some Floor attacks, only lv 1 is enough.
Stake Stockades is great, i maxed it and it still do lots of dmg even in late game, if you use it well.
Looks like Claymore got a buff, i don’t know if this is going to be here too, but i’ll change to lv 8 on mine later.
I found collar bomb great, but only for Plate Armor enemies. Not disappointed with it at lv5
Punji Stake is… eh… something. Lv 1 just for fun. :v
If you like PvP, Conceal would be good, Sapper Traps got a huge buffs for the Traps on Arena.
And of course, Broom Trap at Max Level, this blender is so good for grind.