Says the noob giving advice to beginner.

Look op. If you wanna buy a barbell, make sure you have the proper other equipments ex. Bench press station, squat rack or power rack.

And standard barbell weight (bar alone) is 20kg. Should be a good start.

What I'm saying is, without these equipments, you can't do much with barbell alone. Only deadlift or maybe squatting at a weight that's light enough for you to clean it off the floor to do either a front or back squat.

If you don't have the moolah to invest in them, I'd suggest you stick with dbs for now or join a gym