Never tried Lab Rats 1, really enjoying Lab Rats 2. Should I try the first one or is it not worth the effort?
Yes, just know that the whole format of the game is more visual novel rather than business sim (which along with different character models did... or does... get this game compared in a somewhat negative light, at least it used to). In Lab Rats 1, you have about 120 days to corrupt 5 characters, more specifically: your mother, sister, the researcher at the start of the game, the teacher at the school who helps with newer serums, and the girl at the coffee shop who becomes a company model in this game (I forget their names right now).
That game is obviously more limited due to time and amount of characters, but if you play it right you'll still likely be seeing new scenes up to the very end (a harem save file I had a while back where everyone was pregnant needed to go all the way up to day 110+ before skip to end would work), it's really good but just know that it is not the same gameplay loop as this and aside from some general references is not needed to be played before this game outside of basic "you used to work in a chem lab at school and knew some people, now you want to start a business and they remember the summer you were with them... kinda".
I don't know if the walkthrough still exists on the original post here, game released way back before F95 went to new servers so old walkthrough location was dead last I checked, but I do recommend it if you want to see unique scenes like what character responds to what at the beach, and finding the red and purple serums and how to use them.
If you played this game and thought "I want less business stuff and more character focus", definitely play the first game.