post your buget, please?
pbn is not cheap before silly budget
don't forget pbn are not just in ones, pbn are about the power of the main keyword.
you said
gamble industry
this will cost a lot for each pbn, it the most wanted and used kw on the .net apart from sex adult stuff.
easy $5k to start with to get anywhere up there and that a crappy sub keyword.
people are throwing thousands daily at gamble industry keywords.
you need proper powerful links in there,$2k month to hit the top of gamble industry.
not joking.
ps.
I would use Google AdWords, bing to see if you can profit from any keyword you no, then think about pbn's I promise there not going to be cheap.
your need constant written articles and constant heigh links the competition is mad.
gamble industry
is not easy to earn it a hard game and takes huge money in promoting keywords to earn.
the problem in that industry is no matter how small the keyword is right now you get big companys to slap high bids on it to use in AdWords, bing, it very hard to find low priced anything in the gambling industry.
I wouldn't use google website for this I would go to gambling chat places and promote and just use a landing page with a deal on.