Gonna disagree, but only because it is specifically a new player problem:
Green gear effects, are VERY situational, and very diverse in makeup. Most of the secondary effects are based on temp conditions("…after taking shield damage" “…after surviving for 180 seconds”) I advocate for blues and purples, in particular purples, mostly because their effect last longer and are more focused. Something that grants you two effects the entire game, is far more valuable than something that grants one permanent effect, and a temporary one provided you fill in a condition first. And while Blue gear items may have temp effects, most of those will correspond to what that kind of gear does in game. It’s not always perfect, but it’s easier to see and feel in game, how X and Y add up to give you Z benefit when the numbers are a constant.
Capture games are an exception to this rule mostly because, as you said, there are precious few shards in that game. Largely, I don’t both trying to build gear in those games, because they won’t go on long enough to make the effort worth the result. I’d rather put shards in that short gametime, to things that slow down and delay my enemy, more than help me over the long term. And accelerators and turrets don’t just hinder my opponents, they grant me XP for building them.
As a new player however, it’s very easy to get overwhelmed with gear choices, so I offered advice that was simple, and easily expanded upon as bubreg gets better. He’ll eventually find his groove with items, and start to evaluate things more on his terms. If he wants to go for more speedy builds that finish early or more expensive ones later on, I think he’ll find his own way.
As far as the Red text; until you have seven or eight gear set slots unlocked, you can’t really dedicate them to specific things. Most will be changing and adjusting gear each time they play, for different effects. They may rotate through three and four different versions of a DPS build, till they decide how they want to run one. It’s HORRIBLY easy(I speak from personal experience of course 
) to forget that red text actually DOES affect you if you say pick characters that have a shield, or reload their weapons. So, until bubby had a good grasp on the gear, I suggested him leaving those things alone. Red items aren’t bad, and I know people who swear by zero cost gear sets to get that early jump. But those are finely tuned sets, and it’s easy to go out of their profile and get hit with some big problems IN game.
