your strategy depends on your budget.
Do you have unlimited budget? Buy (quality) PBNs, niche edits, and guest posts for each page you are trying to rank (including the homepage), gradually over several months until you rank.
Do you have limited budget? Divide it by $7.5 (because decent quality links usually sell for $5-10 minimum, so we take the average of $5-10, which is $7.5) to get an estimate of the number of links you could get with this budget.
Then take the list of keywords you gathered and analyze them to see which ones are easier to rank. If you have, let's say, 13 keywords that are easy to rank for, split the number of links you can get with your limited budget between the 13 pages you're going to create for those 13 keywords, saving about 20-30% of the links for the homepage of your client's domain (google favors big brands and strong domains, so you'll want to gradually build the strength / authority of your client's domain while building links to the inner pages, which is why you'll be pointing 20-30% of the backlinks to the homepage).
If your budget is too small to be split between multiple URLs... well... I don't know then. Maybe tree free backlinks (web 2.0s)?? But these are shit, so...