I don't think going off the meta is a bad thing, but I will definitely say that there is definitely a limit on just how much deviation there can be on a champion's intended builds and uses.
Example: ad vaigar. Sure you can try it if for some reason your team has a lot of magic damage and maybe only 1 physical damage doing champion. It might be worth it because your team might need more physical damage to counter the enemy team building high magic resist. At the same time though veigar's abilities all scale with AP, meaning that perhaps aside from event horizon and his ult, the other abilities are going to be sub-par in damage even with his free-ap Q ability. If you can actually get it to work, well then super! If not, well try explaining to your team what your intent was and that you were trying to counter the enemy team's build.
then we can have an example like this: AP Talon. All of talon's damage scales from AD, not AP. Not only that but without something like nashor's tooth his autos will do horrible damage, and even then none of his abilities will do any significant damage either. This is what you really call a troll build or even intentionally feeding because you're not helping your team with this, you're hurting your own team and helping the enemy team by giving them an easy fight and very likely an easy kill.
Before you try something unorthodox or off-meta, please do consider a few things to help you decide if something might work or if it's worthwhile:
- what is it that you're actually trying to do?
- is this going to help me against my lane opponent?
- is this going to help me later in the game when we group?
- does my team need a certain criteria filled to balance out our roles? more damage? maybe more cooldowns for crowd control? tankiness?
- what is my champion and what does the champion's kit do or revolve around?
remember that you're not just playing by yourself but with 4 other people on your team. Don't forget they're there to try to have fun as well so don't ruin their time by hurting your own team's potential.