Your level
Artengo has three types of tennis bag that fit for different playing levels:
For occasional players
If you are just starting out with tennis and play occasionally (once a month max) then you simply need a travel cover or a single racket bag. You will essentially be looking for a bag which is both strong and light.
For regular players
If you play tennis more regularly (once a month to twice a week) and you are hoping to make progress, then a 2-racket bag would be suitable for your needs. These bags also have compartments for shoes and accessories.
For intensive players
If you play competitively and you practice several times a week, you will need a bag which can hold up to 8 rackets with compartments for shoes and accessories as well as reinforced straps to make it easy to carry.
Why not a backpack?
If you don't want to be weighed down with a travel bag or carry cover then you could always try a rucksack. The advantage being they can hold up to two tennis rackets along with all of your accessories. They also have lots of different compartments. The extra storage space is super handy for moving from place to place.