Like l said, its my first dirtbike & l was thinking about buying a no-name brand bike but l dont know. What should l get. l have about a 1000 dollar bughet.

A great bike for u would be a Kawasaki KX 100. It is a smaller sized bike but it is a 2 stroke so it is got a good amount of power & torque to keep u excited for the next two year or so till u need a bigger bike. Make sure you've got an experienced rider with u when u first test this bike out because it is a zippy little thing & will take some getting used to but for the price, size & power I'd say this is a perfect fit. You could get a 98' or 99' for $1,000 or under depending on the hours & the condition of the bike.
take a look at the ad below.
Another bike to consider is the Honda CRF 150 F. This bike is more user friendly because it is a 4 stroke so it has a smooth powerband. See the ad below. It is a little more expensive but u could probably find one for around $1500. It just depends on if u want a faster bike that you're going to use for longer (the 100) or if u need a beginners bike that is smooth trail riding but a good amount of power.
You should test ride both to get an idea of the difference in power & size.
Good luck!
DO NOT BUY A NO NAME BRAND!!!! That is one of the biggest mistakes ever. l bought a 2002 ''Loncin 150'' brand new & it was the worst bike ever. l sold it & got a Honda XR200.

If you want it to be fast get a 4 stroke, a 2 stroke is fine but it is not as fast as a 4 stroke. l am 5feet tall two and l would get a 150cc or a 200cc. If your not going to buy another one in about a year and a half, than get a 200cc engine. It will be 1000$ - 2000$.

As Jenn has said u would be doing yourself a disfavour in buying a no name bike as they r trouble. Once something goes wrong with them & it always does u cannot get parts for them. Stick with the well known names & u cannot go wrong.
For ur height l would suggest a crf150f which is more of a trailbike unless u intend to race. If u do u would be better off going for the race version the crf150r or a 85cc either a kx85, cr85 or a yz85. Or again if u r just looking at a bike to knock around on a Ttr125 or klx125 would suit.
be very careful buying a bike with only $1000 as u do not get much & really l would save more before buying & buy a better bike. Go to some of the dealers & sit on a few bikes to see how they fit for size.

get a ttr 110 is about 1800 a little over but a very fun and fast bike

Find some one with a old old rm80 like a 1989 or so. practice riding it then buy a bigger bike like a yz125 or rm125.

A 501 Maico makes a nice first bike.