Which filament the best one is to buy, cannot be answered generally. Certainly the crucial aspect to check is the filament thickness. It must be considered which is the right one for your printer.
There are two common sizes: 1.75 mm and 3 mm. Before you buy a filament it is recommended to ask the manufacturer of your 3D-printer for the best size.
Every material has its advantages and disadvantages. Especially in terms of heat resistance and stability PLA and ABS are great. Again, you should decide before buying the filament what you want to print with the filament. After deciding you can choose best which one to buy. On Amazon all the materials are available. They vary in color and price. Buy the filament in your favorite color, to give it a vivid look, so you have even more fun on the print!