I admire the enthusiasm but perhaps that’s also your problem starting out. Might I suggest focusing on one thing at a time. If you have a favourite character or a favourite story arc of some significance, dedicate yourself to that first. For example; let’s say, after reading 52, I now want to contribute to the Database. It’s an event that covers a whole year, with multiple characters in multiple story arcs. Where do I start? I’m not going to start at the beginning and add to every character’s bio on an issue by issue basis. That would be madness. I’m going to pick ONE story arc of the seven and ONE character from that arc. Isolate the issues that character appears in and write a draft (on a document you can save, not the edit page of the Database) until you’re happy with it. Make sure you edit yourself, which is the hardest thing to do in the moment. I’ve looked back on my contributions at times and seen obvious fluff I could have excised the first time. Always remember that bios are concise. If you want detail then write an issue synopsis.
Let’s say I choose the space castaways arc with Adam Strange, Animal Man and Starfire, but the character I choose is a more minor role, Lobo. I don’t need to mention everything in the story leading up meeting Lobo or how Starfire is aware of Lobo because he was once active in the Vega System, nor do I need extraneous details like how he rips off her top during negotiations. You’d only need something like;
As a priest of the Church of the Triple Fish God, Lobo took a vow of non-violence. During this time he encountered three heroes of Earth stranded in space. He agreed to aid them, only to lead them into greater perils of a decapitated god and the Lady Styx. After finding a loophole, Lobo abandoned his vows by fraggin’ the deity he formally devoted himself to.
If people want more info they can click on the character links or the synopsis of the issue cited. As far as the bio is concerned, that’s essentially Lobo’s environment in 52.