I've started to graduate from Silver to Gold, but if you've got very low level characters appearing during Gold matches, bear in mind sometimes you search for Bronze to level up your character and it throws you into a completely random match (I've got Platinum before, and suddenly appearing next to two Banshees is no fun at all).
Having said that, if you aren't an Uber-Leet player (like I imagine everyone in this thread is) then their are several things you can do to do much better in Gold.
Make sure you've maxed out your common mods and weapons, and this is simply done by buying recruit packs. Get some better (or at least different) weapons by getting Veteran packs (and hopefully pick up some gears).
If you don't have all the uber Ultra Rare guns, play a support class (Infiltrator, Geth Engineer, etc) or an Adept and play at a high level (18-20).
Equip a decent assault or sniper rifle with the piercing and damage mods. The Mantis X is a decent sniper rifle. If you've got a Mattock, that's great as well.
Set your character up in such a way that they can cause tech bursts or biotic or fire explosions. These are great for crowd control of lower level enemies, and aren't fun for bigger enemies either. They also don't require awesome ultra rare weapons, just the right ability combos.
Here's a good place to start.
http://masseffect.wi...ki/Power_Combos
For players new to Gold, the most important thing to do is stick with the group. If you go off on your own, you'll get overwhelmed and killed and someone will have to come and revive you, and frankly if you are the other side of the map, and have been running off to the other side of the map every wave, and other players have got killed trying to reach you before, then no one is going to come for you because you've proved yourself to be a liability.
Stay with the team, revive other players, and if you have the worst character, then cap the objectives or carry the pizza.
The Mass Effect wiki has detailed player notes on each class, simply scroll to the bottom of this page and click on the class you want to play. It goes through how to cause explosions, if they are possible, with each character as well as suggested load outs.
If you do want to play Gold, then try the character out in Bronze and then Silver first (these two games should also net you 40k credits, enough for 8 recruit packs or 2 veteran packs if you still haven't maxed the common weapons or mods or built up enough of a pile of consumables).
If you are reliably causing explosions with a power heavy character, then you don't need to worry too much about uber weapons, because you only fire them when you're waiting for your powers to recharge, and if it is a very light common weapon then you'll have a recharge of +200% and be spamming powers.
You do want all the mods. Different weapons work well with different mods (so a Mattock with assault rifle piercing and assault rifle precision scope doubles up as a semi automatic sniper rifle) and having them at V gives the greatest effect.
Very simply, think through your character, don't go in gold until you are finding Silver lacks challenge, and go in with decent weapons and equipment designed to fit around what your character needs to do.