Buy what nobody recommends but make sure it's not total junk.
Best coin to buy probably isn't on polo though because coins listed there are pumped already. Polo-coins are actually higher risk than those not listed there after all these months of pumping.
But that's the thing, they're all junk. It doesn't mean it's impossible to profit from any of them, but you have to get in and out quickly. Frankly I wouldn't touch any of them right now.