I have also used cardboard under wood chips as a way of building soil while stopping weeds such as oxalis. Many choices There are many choices when it comes to mulch. You can recycle your cardboard and build soil by laying inexpensive wood chips over the cardboard. Wood chips are usually available from your local tree surgeon, sometimes for free. Raking leaves from under trees is sometimes not necessary especially if you are just going to replace the leaves with mulch.
Leaves can be a mulch.
Even grass clippings can serve as a quick mulch. Be careful when spreading mulch not to get it right up against the base of plants or trees where it could cause rot. It is best to leave a few inches around plants. I once made the mistake of using a compost made with rice hulls as a mulch for a large area. The wind blew the rice hulls into the neighbors' yards.