Hi, first of all i am not an expert here, but I do have some experience in it. Last time I used, I started with about 60 keywords and then narrowed it down to 40, then 20 then to the last 6-7 best performing keywords. If you don't check the keywords performances from the early beginning, your campaign quality would drop down. So, even if you start with a 100 keywords, make sure that either all of them are performing well or just narrow down your keywords to a few best performing ones before your campaign quality drops down.