It's easy to buy more shares for yourself. Go to your wallet, then 'transfer' to steembasicincome and put in how much Steem you want to spend. In the memo line put in the user name of the person you want to get a share. If you buy 3 shares you can put in 3 names, separated by commas. If you buy 20 shares and put two names on the memo line they will each get 10.