Q:

word for the act of each person in a group put in some money combined to buy something

What's the verb/phrasal verb to describe the act of giving/putting in a share of money towards a total amount to buy something as a group where each of the other members in the group put in their share as well, like buying a lottery ticket as a group or some other purchase. I.e. "we all _ for the lottery" or "everyone _ $2 for the lottery ticket"

A:

Pitch in (“(idiomatic) To help out; lend assistance; contribute; to do one's part [eg] If we all pitch in, we can raise enough money for the renovation of the church”) sometimes is so used. 
Also consider ante up in its “To contribute one's share of a payment, or to pay what is due” sense, rather than  “To pay a fee necessary to play a game, typically a card game”.
Some phrases that work in the first example sentence include  buy in,  chip in,   pay your share, and do your bit.  Three of these don't work in the second example, however.

A:

While the suggestions already mentioned are most common (pitched in, anted up, kicked in) you can also say "we pooled our money to buy a gift".

