I don't think you are listening to what you are being told in here.
A 125 is probably too much bike for you.
If you insist on getting a 125 , be aware that none of them really have alot of bottom compared to a 250
When a 125 gets revving, it produces A LOT of power.
To create more bottom end in a 125 you need to lengthen the intake tract between the reed block and cylinder.
Moose racing makes an aluminum spacer called a "TORQUE SPACER" for almost every 2 stroke ever made.
They cost $30
This mod alone will give you great bottom end for cheap
Your other option is to lengthen the exhaust tract after the port
FMF makes a pipe called the "GNARLY"
It produces a ton of torque and is made out of 18 ga steel so it's tough
It costs $200
It will work with the stock silencer
HOWEVER
If you are going to be trail riding you should also equip your 125 with a spark arrestor
FMF makes 2 great models that do not rob power
Turbinecore 2 ($120)
"Q" ($150)
The "Q" is a little more expensive but it is quieter than the Turbinecore, which is a good thing.
Loud bikes, although assumed to be faster, are not as fast as people think.
They only seem faster because the rider is subconcsiously scared by the loud sound.
It is a natural reaction that you have no control over and has been scientifically proven.
The loud sound also pisses off nearby people that do not share your love of dirtbiking.
The combination of of these items {torque spacer+Gnarly pipe/SA) and the addition of an 11 or 13oz flywheel weight
($110 from stealthy)
will give you a ton of bottom end and will smooth out the power delivery throughout the entire throttle range.
GOT IT?