Defiantly a red eared slider. They are very easy to look after.
You will need a big tank with a shelf or a floating island for basking. A uv lamp, a heater, thermometer, filter (they are very messy). avoid using rocks it will end in tears they like to wreck things like your glass heater will need a guard around it or it will get smashed you can get stainless steal ones now but they are costly. All in all they are very easy pets to keep and are a lot of fun