Need counseling advice

Hi, I just started working on a digital marketing company. What we do is, all the white hat techniques. I think I have already grind them all to there limits. Also I have done all the On-Page SEO that I could do and all my pages have 2000+ words good quality content. I am targeting only for long tail keywords with low or mid competition still, the site rank isn't improving, it's just stuck at one position, not getting the desired leads.

I was thinking of doing new approaches and for that I have read a lot on Contextual Link Building. But I am totally confused on what to do and how to do it in cost effective way. Some says, this-that methods won't help you and it can hurt you in a long run. Some says that it's the only method to achieve anything on SEO. I am confused in what direction should I go for.

What techniques/process digital marketing company usually do for pushing their rank and get effective results in a cheaper way?

I need help from an expert/counselor. I don't have much money to spend and this covid situation has already made it worse for me. Any advice you could give, would be much appreciated!