A 10 gallon tank is a great start, just keep in mind that it won't take that many fish.
If you got it second hand, you need to check that it doesn't leak before you use it. I generally do this by sitting the tank in the bath/shower, then filling it with water till it is full to the top and leaving it for at least 12 hours. If the water level drops, then it is leaking and needs re-sealing.
If it is new, there is only a minute chance that it could leak, so I usually don't check new tanks.
I hear you have a male Betta? In my experience they do best in 5-15 gallon tanks, so it would be an improvement if the acrylic (plastic) one you have now is small. Also glass is slightly harder to scratch than most acrylic.
For a beginner, the bigger the tank, the better as water parameters are easier to maintain in a large tank.