To charge it in the time it takes with the original charger, use one that has at least the same number of mA on the Output line on the label. Since most phones and tab;lets won't accept more than 2 Amps, and most decent charges today are 2 Amp. that works out well. (If it's set up internally the same way that Samsung devices are, you should use a Samsung charger, since they wire theirs differently to tell the device to draw more current since it's on a charger, not charging from a computer.) Try
Galaxy Charging Current Lite with the original charger, and you should see how much current it draws. If it draws less with the charger you use, it'll just take longer to charge, it won't harm anything (except, maybe, your patience).