When should I begin testing?

Jordan
Had my Nexplanon removed in January and since then cycles have been anywhere from 27-37 days. This is our first month TTC. Bought Clear Blue Advanced Digital 20 pack. According to instructions I could start as early as CD 7 and as late as CD 17. I have enough strips for both. Probably just going to do day 7 and BD most/all days. AF just came today. Hoping to get a BFP this first cycle. But just wondered if anyone had experience with varied cycles like that! And last month when I was just taking OPK to get a feel for it, I had 9/10 high days, never saw peak. But also only tested 1 time per day. But according to my CM peak was probably 3-4 days after I stopped testing. 
Sorry for the ramble. Just excited and hoping for success! Appreciate any insight.