Point me in the right direction

I’m pre-launch starting an e-commerce business (Shopify). Until I start generating revenue and decide how best to spend my advertising/SEO budget (and how much to actually budget), i want to subscribe to a monthly service. Something I can monitor my site, run reports, keyword research, etc. Looking at various companies they seem to range from $15/month to about $180/m. Attracta, Diib, ahref, moz, etc etc etc.

How the heck do I decide?

Thanks much!