Gunslinger Build (Lv. 10-200)

Would adding a point into Dash at the advancement be fine? I'm thinking of doing that because I only need to kill a monster to level again and add 3 Double Fire.

Also, would you happen to know the stats/equips of that godly Valkyrie in the screenshot section?

It won't hurt to add a point into Dash early on if you're funded, but it won't really help much either. Having a bit more damage from Double Fire would be more beneficial in my opinion.

And here's BaSely's stats and gun at level 103..

I think I'll leave Cooling at 25, Gaviota at 16, and max Fire Burner. I have max Inferno on my BM, and I use it often. Fire Burner will probably be even more useful, because Blue Kents and Wyverns will be better training due to better mobility.

Valkyries aren't really meant to train on ice-resistant monsters. If you train there, you'll be limited to either not using summons or getting hit all the time and using a ton of HP pots. Both of your third job summons will remove the stun left by Fake Shot, so the only way to incapacitate the monster is with Cooling Effect. If you train somewhere where you can't use CE, your options will be limited.