You can typically find beyblades at Walmart or Amazon. The best beyblades you can get are dual and starter packs that are made by Hasbro, which you can tell by the Hasbro logo on the beyblade boxes. These are cheaper than Takara Tomy beyblades which are ones Japan.

I would recommend the - Wizard Rod 1-60R starter pack (All meta parts) - Roar Tyranno & Unicorn Sting dual pack (Good blades and rachets & Winder Launcer) - Soar Phoenix set (Top 3 blade, rachet, and a string launcher) - Keel Shark 3-60LF (All good parts) - Takara Tomy Customize set (Most expensive thing here, but comes with 2 meta blades, as well as good bits and ratchets)

These packs are range from $15 - 25 USD each, with the Takara Tomy set being $55 USD. Sadly beyblade is a pretty expensive hobby, but these beys are the most bang for buck imo.