For this, we don’t have a specific recommendation. Pretty much every single bot out there worth its salt has a customizable prefix, and the reason being; compatibility. Right now there are so many bots out there, and so many of them have the same common prefix. Being able to change the prefix for your particular server is essential for the bots to work together, and not against each other. Forcing a specific prefix, and an extremely common prefix at that, onto your userbase is plainly arrogant and egotistical. It screams that whoever uses your bot wil value it over all other bots, and that changing the prefix is an “advanced” or “professional” setting that you won’t need. Newsflash; you do need it.