A lapdesk like this one can work but get a tenkeyless keyboard or better yet one of these guys and some velcro or something to hold it in place since keyboards really like to slide around if they are on a moving surface. other than that get a good, big mouse pad (i have the steelseries xl)
other option is steam controller or xbone controller for games that support them but that isnt every game so ymmv there.
probably also going to want to get some usb extensions, if you go over 6 feet i would recommend getting a powered hub. (I have this one.)
edit: what keyboard do you currently have? the corsair lapdog may also be an option if you already have a compatible keyboard.
I also have one of these for general web browsing, watching movies, ect. it works great for that but it is kind of terrible for gaming so you will probably want that to supplement other options, not as your main option.