generally, tri shots are the way to go for shotguns, or those acm, marushin clones that fire 5 bbs per shot and have 3 internal magazines what hold 50 bbs each. But those are gas and expensive.
But tri shots are your best bet, the ones made by DE or the brand stealing ASG.
They are spring powered which means no maintenance required, put in a shell and you're ready to go.
They are generally quite fun to use as i've used one before but they can get tiring because the spring in the gun is a tonne stronger than other spring shotguns, so make sure you have a good left arm.