Been in a guild in Splinterlands comes with a lot of benefits like, an increases % of your DEC earning per battle, a % discount on splinterlands shop, the possibility to fight in brawls with others guilds earning crows, earn merits if you have at least you guild store at level 1 and been able to buy Gladiators with merits, though Gladiators can only fight on Guild Brawls they give you collection power, having collection power is pretty good it increases your SPS you get per day, it allows you to get a superior league that will give you better rewards on Daily Quests and all fights you win.
So by helping level up your guild your will earn a lot more, it is not just paying back a part of the guild is giving to you, is an investment and it is a very profitable one.
And don't contribute 1 single DEC "."
Other post you may be interest:
We Need a New Summoner as a Reward Card: https://www.splintertalk.io/@caimanx/we-need-a-new-summoner-as-a-reward-card