Honestly, once you have Vim, the rest is gravy. If I was doing a gadget maso run, though...
Priority would go to increasing Reflexes to various break points for extra attacks. Guatemalan pepper cannon or Zeno's bow would be gear priorities for the weakening or bonus attack respectively. The Golem's Glock isn't too bad, but overrated, especially when compared to Zeno's. Other important pieces of equipment that may be over looked are Docker's Pants (38 power, level 6, +4 DA) and Carapace Shield (16 power, level 4, +1 DA).
For skills, primary focus would be Basic Martial Arts for the to-hit, followed by Upgrade Armor (superabsorbance for most of the run, resistance for the Mick). After that, I would look at Upgrade Weapons; a lot of people like Frickin' Sharp for the to-hit, but I like Self-Balancing for the fumble reduction and eventual bonus crits. Beyond those (and I'd only put 6 in Weapons), skill points could go as you please. First Aid's handy, and Advanced Martial Arts increases damage. And Metal Detector's always useful, of course.
Personally, I've always been kind of disappointed with the Gadgeteer combat skills. Well, at least since Stun Gas got nerfed back in Alpha. Still, looking at the skills, Stun Gas can reduce to-hit and offense, both of which are handy; they'll hit less often and not as hard. Honestly, the chance to stun should be viewed as a side bonus, not the primary concern. At full points, a single Stun Gas should solidly work over any at-level foe.
Electric Net's been changed a lot over time, but looks like a good candidate for some scaling-type monsters since it reduces their dodge. Sadly, they'll still be able to punch your face in. The damage is... kinda meh, but it'll slowly improve as you level. Not by much though, since it uses square root. The dodge reduction will grow better though. At max, you'll reduce their dodge by a little more than max gas reduces their to-hit, and you'll do some (elemental) damage. Still, reducing their dodge is arguably less useful than reducing their to-hit, especially against the Mick.
Shock Grenade looks to be a beefy version of Stun Gas, doing sonic damage and its maxed reductions being four times that of the gas. At zero points, it's twice the reduction of a maxed out gas. Still, you're trading a chance to stun for sonic damage. The damage formula isn't too shabby, though, doing 10-20 at level 10 with zero points in it. Of course, it's level 13.
If you have access to all your Gadgeteer skills, I wouldn't put points into any of the combat skills. That's not to say they don't have a use, just that you've got better things to improve. Stun Gas can be used if you're a little weak for your zone earlier on, and then migrate to grenade as you reach tougher zones and can better handle the higher PP cost. It's also worth considering using the net against the Troutmaster. In no-items, you're probably using the Bass-o-matic, which is melee, so a -dodge would help. Furthermore, he's weak to electric (at least currently) so the damage would actually be noticeable. A single net would probably suffice, especially if you opened with a stun gas.
Oh, also, Battle Armor is freaking insane. Perm it if you haven't already. Even with no SP in it, 30 + Level defense is amazing.
_________________The churches are empty / The priest has gone home / And we are left standing / Together alone
--October Project: "Dark Time"