There is no doubt there are many toys on the market for cats. But buying a whole lot of toys and leaving them out for your cat all the time will not get the most out of those toys. Many cats will start to ignore toys that they have access to all the time.
A better option is to keep most of the toys hidden away and only have a few out at a time. Changing the toys over every two days increases the novelty of and value of the toys in the eyes of your cat. Some cats will play with toys without their owner present and there are toys available that are designed to work while owners are away. Other cats prefer play with their owner stimulating them with the toys. A lot of cats may enjoy both options.
You can make your own toys at home: people can spend a lot of money on toys and then find their cat is quite content with a ball of wool, a screwed up piece of paper or a cardboard box!
You can also make games to play with your cat. I have concrete floors in my home and my cat’s favourite game is to catch her dry food pieces as they skid along the floor. It engages all of her natural predatory behaviour: she stalks, waits, chases, pounces and feeds.