Cot, blankets, bibs, bottles, baby food if not breast feeding, socks, baby clothes, jakets, coats, tops, bottoms, baby grows, nighties, nappies, bath, bathing products, lotions, mobile for the cot, baby nail clippers, baby boy shoes, teddies, toys, bouncer, walker, teether, teething jel, infacol (for babies who struggle bringing up air, you'll need it!), jug for waming up bottle, bottle steralizer, bowls, spoons, pram, carrier, car seat, box (for toys), bath towels, baby towels, play mat, travel cot?, cotton wool, baby hair brush, baby monitors, changing mat.. thats all i can think of atm. x
You'll need three or four preemie outfits for that first week or two, then 10 or so 0-3 month outfits. Beyond that, it's hard to say until you find out how big your baby is, and how fast he'll grow. Tell your MIL that you appreciate her helping out with the clothes, but the doctor says that your baby isn't likely to be that big, so please hold on to the receipts, or give them to you. It would be a shame to waste money on clothes that he won't be able to wear. If she continues to buy clothes he won't need, keep them(with tags attached), and exchange them, or wait until he has outgrown them, and give them back with the explanation that they didn't fit in the right season.