A couple of little sleeping kimonos or nighties with drawstring bottoms are really nice. That keeps the baby's feet warm. And little stretch suits come in very handy for sleep and for play. Remember that babies grow at an incredibly fast rate, so five or six months is probably the littlest size that you want to buy any quantity of. Baby clothing usually comes in newborn to three months, six months.
Shoes are mainly for show or to go with the outfit.
They're not really necessary until the baby is beginning to walk. Some booties are nice to keep the baby's feet warm.