Best Platform To Create Off-Page Backlinks?

I had a freelancer do monthly off-page SEO for my Shopify dropshipping store and I have no money to pay them anymore. I have their list of quality keywords. What should or could I do on my own to continue the off-page SEO??

Also I've been doing off-page SEO for 4 months and still no traffic to my store but I hear it can take a while for sites to be indexed.