The focus of this build is to make yourself an easy target for the enemy, then overwhelm them with damage from both you and themselves. The bread and butter of this build is the Whirlwind along with Right Back At Ya! Focus on the Dash's quick cool-down and damage rather than the stun duration--the sooner they stop being stunned, the sooner they can make the mistake of counterattacking you.
Begin the game with the base Dash and Whirlwind abilities (Piggy Bank should help buy them both right at the beginning). Combine them both to help you collect Solar, then get Can't Touch This and faster cooldown for Dash. I recommend holding off on getting Right Back At Ya! for a while; if you get it too early in the game, the enemy will have more time to catch on to your ploy.
Start off by dashing into enemies, then immediately go into Whirlwind. Can't Touch This will keep you from taking very much damage, and Right Back At Ya! will send the full damage right back at your enemy. Once they realize their health just disappeared, they will try to run: by this time Dash's cooldown should be done, and you can use it to catch up and finish them off with your fast-shooting gun.
The lack of speed gives you a good opportunity to "fake run", goading your opponents into chasing you. Once they get within range of your Dash, you can hit them with the above tactic.
Dash: Golden Watch, Clock Necklace, Hydro Smash
Whirlwind: Can't Touch This, Right Back At Ya!, Bio Fuel Cells
Gun: Pirhana Cartridges, Thorn Fish, Mutant Worms (either of them)
Standard Upgrades: Piggy Bank, Health, Regeneration