I'm not actually sure what you are and are not doing, but I can list some things I see people frequently doing around silver and gold that cause losses.
If you're top or bot and a tower goes down, the laning phase is over. It doesn't matter if it was yours or their tower; laning phase is over. At this point, just push the wave till it goes the other way and head mid. Even if it was your tower that went down, trying to take their tower just makes ganking you way easier. Only try to take their tower if you know where every member of the enemy team is and it's nowhere near you, or you have the cooperation of your team to help you take it.
There are limited times when it is ok to jungle. Do no jungle if you are next to a minion wave that is pushed your way and nobody on your team is pushing it back. Do not jungle if your team is preparing for a teamfight. Do not jungle if you are not the jungler and it's still the laning phase unless your jungler specifically ok'ed or asked you to. Do jungle when it comes to taking the most logical objective available. Do jungle if every wave is pushed towards the enemy and your team is mostly back at base.
Group up as much as possible after laning phase is over. Split pushing is a valid strategy, but grouping as 5 is better the majority of the time. Split pushing is really dangerous unless the split pusher has some skill that allows him to join his team should a teamfight break out.
Also, this isn't really a mechanical thing, but abusing dynamic queue makes climbing easier. I personally prefer to play solo, but there is no doubt that premades have a significantly bigger advantage. Treat solo games like interviews. If you see anybody that carries that game on either side, suck up to them and add them after game. Then see if they'll queue with you.