Newbie dirt bike rider. NEED OPINIONS?!

So i recently (2 months ago) started to ride my friends 2 stroke honda cr80. This was the first bike I had ever ridden with a clutch. I have gotten used to using a clutch and shifting etc, and I generally feel very comfortable on this bike. Now here's the problem, I am way to big for this bike. I am 5'9" and weigh 180lbs. I am buying this a bike for myself sometime this summer and I was considering buying a 4 stroke 250 (a trail oriented bike) do you think this is a good or bad idea considering my experience. Oh also i should add that i would be learning how to ride this bike in a big empty grass field. Feel free to ask any other questions you have. Anyway thanks for your help.

Read more: Newbie dirt bike rider. NEED OPINIONS?!