First of all, I wanted to give a big thank you for the feedback provided. I was looking to start a similar thread myself, so found a lot of pointers here helpful.
To OP: If you just started, I would stick to bronze until you feel comfortable with the game. It is quite different than single player. Recruit packs are cheap and maxing out your starting weapons will make you sufficiently equipped for silver once you are comfortable with game mechanics. Stick to ranged damage until you are comfortable with boss mechanics, map layouts and spawn locations.
To other readers I would like to hear your opinion (I am slightly more advanced than OP, generally have tier 1 or 2 of most weapons and only a few kits still locked):
Big Question: What do experienced players consider a passable level for a random PuG in a gold group? 50% below top scorer? 66%? 75%? (Note, no scorewhoring assumed, nor damage from missiles)
Small Question 1: Having tried AIU and enjoyed shotgunning things into face, I was wondering why people prefer Claymore to Raider (at least on silver). I suspect that on gold+ due to damage resistance one big shot > two smaller shots even if the net damage of the two shots before DR would be greater, however I am not sure why this is still used in lower tiers.
Small Question 2: Is there any way to measure the connection speed to host before starting the game? Running Valkyrie and getting sync killed by banshee outside of extended AF range is not the most fun moment in the game. Would like to avoid those if I can! Also, how often do people end up KOed with repair matrix active? Is this just latency? Seems like every other time lately I hit Repair Matrix, get KOed anyway and just lie there with nice green faceplate and minus one charge.