Three seeds is nothing, you'll probably observe no effects at all - but you should still try it for the first time, to see if you even find all the nausea that comes with it worthwhile. If it's good, you can try something between 5-6 seeds the next time and see what that does to you.
Overall I wouldn't recommend spending too much time on LSA, you might find it very interesting, but it's no where near the real deal.
Everything this person told you is highly questionable.
I wouldn't trust it at all.
You already heard the story about the dosage. Can you imagine if you decided to take 5-6 seeds this time, listing to him/her, and you had the strong ones? You might be really, really surprised.
As for "it's nowhere near the real deal", that is clearly spoken by someone without enough experience.
If you take the right amount, you can flyyyyyyyy, just as high and far as on on a high dose of LSD.
I have nearly 25 years experience with psychedelics. I have done LSD more than 50 times, and HBWR at least a dozen times, including a few of the strong experiences that are equal to strong trips on LSD. Trust me on this one.
Finally, I used to take the seeds ground up, and often experienced nausea or other unpleasant physical symptoms.
But with a water extraction, I had no nausea or other unpleasantness at all.
I highly recommend doing such an extraction.
Read up on some experiences on Erowid, and you will see that people generally get really bad nausea, which can be enough to ruin half their trip or more, but with a water extraction there is generally little or no nausea.
Good trippin'!