For reference, my team is currently gold 3, not amazing, but enough experience to give some handy tips.
Tips:
Don't get behind and kill nexus. You're well on your way to become an Osu Champion!
Oh wait, wrong game, anyway, vision is extremely important, once you're behind, if the enemy plays perfectly, they'll win because stats and advantage snowballing. But the idea is noone plays perfectly. Vision helps you get back in the game by catching that cocky adc who thinks he's invincible and overextends.
On a side note aswell, just like when you trade in lane with your opponent. You never want to give free poke and harass, so try to not give free objectives either. Most of the time, an objective is gonna go sooner or later, their 5 man is stronger and they are pushing down mid, what can you do? Well you can't def mid outer with 5 men, but you can def mid inner with 4 men. so send one of your guys preemtively to top lane, and while they take a free tower you take a free tower back.
It's all about trading in these situations, don't get too far behind, and look for anything to get back in the game.
Map awareness is absolutely key here aswell, you see 4 men pushing mid, your immediate reaction shouldn't be ALL mid, it should be 'top wave is pushing towards us, the 5th guys is gonna turn up sooner or later, lets make sure it isn't top lane so there's no splitpushing'
To be honest it takes alot of experiance, you've got to recognise at what point the enemy is going to deploy a strategy, luckily in ranked 5's the strategys before plat and gold are pretty linear, so you can pick it up quickly, start preempting.
Another tip: Play to your team's strengths! If you always find your team going behind early game, you've got to respect this as your teams own weakness, so choose a scaling comp, you're going to lose early game anyway, so employ a strategy where you can pull out all the stops late. Then do a few norms together and practice your early game. Iron out these trends you're noticing.
