Assuming that man has a tiny body and normal head and estimating the weigths to be roughly the same size as the head, we can arrive at an estimate of 15000 dreams/balloons.

The volume of a male head is roughly 1329 cc. 1329 cc of lead weighs 15.1 kg. There are 6 weights, so we get roughly 90 kg. This is surprisingly low, and I assume the real weigth would be much more. We can assume the man also weighs 90 kg to offset the lead probably weighing more because of not being round. So probably something like 200 kg if we round up a bit. According to this you need about a litre of helium for each gram you want to lift, so you need 200K litres of helium. According to the same source, we can divide that number by 15 to get an approximation for the amount of balloons we need, which is 13333. To stay on the safe side I would go with at least 15K balloons.