My kids never played with toys at that age. Only sit under a mat for a minute or two. Once they sat they all loved to stack. Cups and blocks are a must.
My son just turned 6months and he loves anything that makes noise or he can stick in his mouth or both! His Fav toy yet is his Crinkle book! it reminds me of crinkling a bag of chips but he loves the texture and sound! it was realitively(sp) cheap at walmart to!
Don't go crazy buying toys for this stage. maybe 5 small, easy to grip hand held toys/teethers/rattles and a couple of small soft toys will be enough. I bought a ton of things and my LO hardly used them. By the time she became interested in toys she actually preferred playing with a scrap of material and a plastic spatula! She ignored all of the fancy baby toys I bought her!
Ever since I brought my daughter home from the hospital, she has lived her toy giraffe. It's pink and soft and when you wind the side it plays music and it's head moves. She used to watch that thing for hours. It's at Walmart.