I have Bambu a1 and should I by pla or petg

For a Bambu A1, PLA is usually the better first choice. It’s easier to print and is great for general use, while PETG is better if you want more strength and durability for functional parts.

I found one Bambu Lab filament in stock, but it’s ABS, not PLA or PETG: White - Bambu Lab ABS Filament - 1.75mm, 1kg.