start low and work your way up.
Couldn't agree more.
If you don't know the exact strength of your blotters (that means and only means: had them lab-tested)
and don't know how you'll react to LSD (aka, it's your first time), you should start with 1 hit. For me it takes quite a while to notice the effects (looked it up in my journal: about 1,5 hours to really notice the first effects, around 3,5 hours before the visuals reached their peak) and seeing how LSD lasts quite long (for me at least: at T+8, which is my last entry before I went to bed, I was still experiencing slight visuals), I wouldn't suggest redosing. Save those blotters for another time, maybe take all three if you feel you're up for it. But you won't know that until you've tried it, so just take one.
If you knew the exact amount of μg LSD in your hits you could make a more educated guess, but even then you won't really know how you'll react to it. For example: my first time taking MDMA (and I got it from a reputable online vendor, so I trust the purity and strength although I hadn't had it lab-tested) I took half a pill, ~100mg and it hit me so hard and sudden it wasn't pleasant at all. Luckily for me I took it at home, alone, so I could just cuddle my pillows and blankets until I felt better. What I'm trying to say is that even at a relatively low/starter dose you can have a bad reaction to a certain drug and you won't really know until you've tried it. There's hope though

: the second time I took MDMA was the other half of the same pill and I really enjoyed it. But I wouldn't want to imagine what would've happened if I took the whole pill my first time, even if I actually had someone experienced and sober at my side to guide me.