I have really low competition keyword with ~8k monthly searches. Right now I built 50 tier 1 web 2.0s(25 expired and 25 fresh). Without any tier 2 or tier 3 this keyword is on 4-10 position, but I think I need tier 2 and maybe tier 3 to be top1. What do you guys recommend to buy for these webs? Just spam it like 100k gsa backlinks on tier 2 without tier 3 and that's all? How many links on every tier should I have?