It's hard to tell you what to do without seeing the actual games. While KDA does not determine victory, it definitely helps. Going 0/7/5 with Nid or 1/9/4 with Siv is a poor performance, and by 42 minutes you should have a full build. Read some guides on lolking and really take the advice given. Don't go into a game with a negative attitude. It sounds cheesy, but say something nice or not at all. League isn't always about getting kills it's about strategy - getting objectives and farming. Many higher ranked games do not have the number of deaths that lowers one do and for good reason.
If you're jungling learn about optimal pathing and warding. If someone is being pushed to their turret then most definitely gank for them.
If you are an adc learn to read your opponents and your support. Is your support a sustain or tanky cc? Are you a kill lane or passive farm lane? Knowing the answer to these questions will help you in the laning phase.
It is not usually a good idea to initiate without proper wards. Many people just want to play the game for the glory of getting kills but you can be easily punished for being greedy. Make farming and objectives higher priorities than getting kills.
In bronze I would recommend the following: always put the same role as your primary and the same role as your secondary. Pick no more than 5 champions to play in that role (1 or 2 would be better). Master playing them and you will know how to play them against a number of different champs.