How many squirts of ADA?

Step 1 for the first 1-3 months. Then move to STEP 2 for the next year. There is no "one-size fits all" dosing regimen, because systems, scapes, species chosen, etc. all vary. No system is purely a "read the bottle and follow the instructions like a robot" one, and ADA is no different. Though ADA instructions are more thorough than many I have used and they outline use, amount, and frequency reference points quite clearly. An example of the regimen for an "average tank with a variety of species/plants types" is even given.
Brighty K from Day 1, and the core of the line is Brighty K and Step 1 or 2. Brighty LIGHTS I find myself using very little, except in my heavier stemmed plants tanks and any layout where there's lots of glosso or Riccia (2 plants I personally do not work with much right now). I am not big on N and P myself either in most layouts-- never have been. When you look at ADA tank specs, it's pretty much Step 2 and Brighty K, and ECA. Green Gain after trimming or stress. If I perceive a Nitrogen/Phosphorus deficiency, I do then come in with the Brighty LIGHTS. If you are more accustomed to working with macros, then you likely already have better understanding of how when and where to use them and can incorporate Brighty LIGHTS accordingly.
Frequency-wise, you can go as much as daily or as little as 3 times a week. Again, it will vary depending on your layout. It's like anything-- you get a feel for it and work from there. Generally speaking, the liquids are designed to be used more frequently-- not so much a "just add after water changes" system. The idea is to provide a steady stream of nutrients, something to the effect of adding what the plants are using in a day or two.
I have found that cutting back a bit from the recommeded mount in the early stages is fine, especially when using ADA substrate. The idea (and assumption) is to use ADA substrate which is providing a generous amount of nutrients to the water column early on as well. I have always been from the keep-it-lean school anyway. I very very rarely have algae issues of any kind. I find it is easier to spot a minor deficiency early on and kick up the nutrient accordingly rather than over dose based on over-adherence to package instructions or following too closely what worked in a different tank or for some other person's post (not knowing fully the details of their system/regimen) and then having to deal with the problems that result from that.
Once I got a feel for it, I really like the ADA ferts because it is very easy to dose and I do know that the necessary nutrients are being provided. My tanks where I use ADA regularly and exclusively are all in optimal health. The composition may have it's issues (trust me, I don't post way more tanks than I do post for that very reason), but the health and balance is clear.

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