Thanks, the shops aren't offering second upgrades to me yet -- I just meant buying the first $600 upgrade but for all weapon types.
What's the recommended point to stop doing side missions in playthrough 1? I've just opened the road barrier and am being sent after the wasteland boss (Sledge?). The job board just added optional missions to find recorders and gather crystals.
I would do all of the bounty board missions/other missions available in Arid Badlands.
After you beat Sledge, you get sent to the Dahl Headlands. At that point, I tend to stick to the story missions, crystal side missions, and all of the claptrap missions, of course (for the extra backpack slots).
the problem with the game is that you can become overleveled rather easily. the general idea to keep the game challenging, is to finish play through 1 ~level 31-35, then playthrough 2 ~level 50-51. Then, do Knoxx DLC, which has the hard level start of enemies at level 51, I think.
AFAIK, you don't have to complete the final mission on PT2 for the level scaling to kick in across the game, you just have to activate it. I don't think there is level scaling in Knoxx until you finish the main mission.
but, it's all up to you. I thought it was stupid to have to play the game twice before doing the DLC, but I had enough fun by the end that I just wanted to do it again. :\
and yeah, go ahead and buy the first weapon upgrades if you want. I forgot to mention that each successive upgrade actually gives you the max allowed at that point--so if you skip one upgrade, you will still get that increase in ammo on the next one, without losing the cash from the previous upgrade. That's the real issue with holding off; can't believe I forgot that, haha.
I would stick to the weapons you use the most, of course. Then wait till later and get the single high-end ammo upgrade for your other weapons.
do take the time to search lockers. I often find strangely good loot in those--one of my max merc mods was in one.