get L b full license, then find second hand z650 or cfmoto 700 clx, both used price are lower than a new z250

if you think 650 cc is too much for you then can try used dominar 400

you are already used to clutch moto with rs150 so getting 250cc big bike is kinda pointless

I'll suggest some naked bikes within your budget, imo z650/er6n should be your baseline bike

Kawasaki er6n - the bike you will find used in training for B full at driving schools (although some schools have start using z650). old and heavy but not hard to handle. easily can find one under 15k

Kawasaki z650 - can't go wrong with this one, lightweight and small size like a 250cc bike, engine has enough power for highway but not too much that it will scare you, cheap with the reliability of a japanese bike

CFmoto 700 clx - neo-retro design. you'll probably like it since you like cb650r design. the engine is based of kawasaki 650cc so its not bad and easy to use, some of our users in here reported some problem though.. also its front 18" wheel will probably make finding tires a bit troublesome

Suzuki gsr750 - awesome inline-4 naked bike, older model of the current gsx-s750. I had a gsx-s750 upgrade from z250 and I'll tell you the power is not hard to handle. its linear power delivery makes it easier to control.

Kawasaki z900 - another inline-4 naked bike, 950cc naked bike. probably wont need any other bike when you have this. this one is not really beginner friendly though but its easy to get used to. you can find used under 30k


Also try and sit on these bikes if you can and ask for test ride.

unless you are planning to bring your wife for ride, keeping L for B full a year is just RM 120.
then you can make B full license at PS samy at kkb for about RM 700, you can ask about it at their branch in batu caves.

renewing license is all online now anyways so theres no hassle.
get that er6/z650