it's far better to make a mech that can win without kits... put if someone is going to pull out kits on me and they'll beat me just cause they'll use kits and I won't.. then I'll pull mine out and put em in their place.. kind of a personality choice I guess haha.. but 95% of the time I would say you shouldn't really be using kits... also try to make one really really good mech at lvl 22 or whatever and stay there till you can get another.. don't go on with having lots of mechs but they're all just not that good..
Definitely the plan. I've already figured out trying to have bits and pieces upgrades at a time is a bad idea.
As far as kits - I win without them if I can, but if I know I can win the full credit award by spending 700 on a repair kit, it's worth spending the credits for the win. More expensive kits (like resistances) I don't use. It's purely a matter of cost/benefit - although the extra win count is nice too.