I tried "Parker" , I did the one time package together with monthly subscription. The monthly boost was good, but the downside is it only occurs once a month! Means they only work on my website once a month, supply a group of backlinks and that's it. It's too slow for my liking, rather buy or subscript to some softwares and do them myself on a daily basis. My advice is invest time and do it yourself, saves money and most of the things you could pick up on this forum. If you don't mind waiting and it's not a competitive niche(no one using PBN and such) then you could try his monthly subscription. If you would to see results faster and it's competitive, do it yourself.
Remember all SEO services are the same, you are not their one and only clients. Expect that they have multiple clients and they work on each one according to their timetable. No one has the utmost interest for ranking your website as much as you.