You can only increase your skill level by playing Ranked matches. (lone wolves, team doubles, team slayer, squad battle....)
Play them and win. You get better chances of raising your skill if you have a high positive K/D Spread (more kills than deaths) AND if you beat higher ranked opponents. Your skill level may go down if you lose against very low ranked opponents OR if you constantly keep losing in a row. Once you get to 35-45 skill level, it becomes very difficult to increase your skill. So let's say you have a 45 skill, you must almost win about 2-4 games in a row in order to get to 46. I would recommend playing lone wolves because top 3 high scores gets exp. If you keep winning either 1st, 2nd, or 3rd place in a row in lone wolves, your skill will increase.
It took me about 4 games to get to 45.
Anyway, it depends on how good you are.
Good luck.