With a little imagination, store-bought toys are not necessary but there are lots of interesting ones out there. Just ensure you buy those that are sturdy and check the toy periodically to ensure no parts are dangling etc. Leave an empty cardboard box out and around, they love to sit in them - remove all ribbons, tape, staples etc. Cellophane or paper crumpled in ball sizes. She bought a very cute fountain that from a local department store.
Periwinkle loves to climb up on the stand and drink from it.
Heather says that Gizmo loves to play with plastic bottle caps such as the ones from 2-liter Pepsi bottles. All of Cynthia's 3 cats love to play with pull-off tabs from milk jugs. Mary-Beth's white cat, Cueball loves to play fetch the tabs with her. Of course, the tabs usually end up under the furniture. Sally's Ragdoll kitten, Jasper, loves to bat around a drinking straw that she ties in a loose knot.