i been trying to find for you a site that would help more with what i was about to say, but each month the neopets magazine has some weird puzzle in it and if you enter the answer to the puzzle on the site you get neopoints and can somtimes be given a free codestone. Obviously you dont need to buy the magazine as most neopet fansites post the answers for each month, (theres currently about 7 issues with these answers which can be entered online which means 7 chances to get codestones), im sorry i cant find any links, i just spent half an hour looking! if i find any i'll be sure to post back
i think there are monthyl freebies you can get too which consists of 2k and 2x codestones. not exactly sure of the link but i think its something similar to www.neopets.com/freebies or somethin like that. accounts must be at least like 1 week old i think.
no the accounts have to be at least one month old and are given 2k and a food of the neopets choice. No codestones are given out.
but the key quest is a good way to get some though, i got in average 4 codestones with 6 keys! , otherwise, aber is the best way to get them cheap
yeah, auctions is where I go normally, saving for that elusive auction sniper. Until then, its all manual. XD