To effectively key you're going to need fast reaction times, the ability to memorise the map and locations of doors, and high non-combat skills. Since you're on a mage tank you'd probably need to delegate strength doors to another player. You more or less will just follow the same strategy you do when you solo, except you avoid combat at all costs and have team mates clear rooms for guardian doors, not stopping to help unless there's a particularly strong enemy they'd absolutely need your help with, or if there are no other rooms you can explore aside from what's past that gd. For equipment, since you're f2p and can't get a shadow silk hood, you're going to want the highest level equipment you can wear for defensive bonuses, preferably a plate or ranged top, with your second bind being some sort of weapon; since you're keying you don't need offense as much as you do defense. For ammo you're going to want your highest spell's combat rune, blood runes at your level, if you are going to stay low in runecrafting. If you have high enough rc to make good combat runes, you'd want law runes instead on a typical account. Since your account is magic based though, unless you have range or melee levels to deal damage with, you should probably stick with the runes for combat spells and instead just get high enough rc to make laws.