Yer as said a 125 will be more than adaquate for you, ive been ridding on an off for a gd few years now & have had most varients of bike 125 /250 2 stroke & 4 stroke /450 4 stroke, And am currently back on a 125 (yz) simply because they are cheap to maintain compared to the 4 strokes & are nice an light and have plenty of go heck i still cant use all the power that my 125 offers ...
Get some decent safety gear & have some fun