Choosing the right dumbbell weight is hard!

I recently got a set of adjustable dumbbells after using water bottles for a few months, and I really enjoy strength training, but being new to it, I'm finding it really hard to select the right weight for each exercise in a video.

I saw advice here before to go for about half of what Kelli is lifting to begin with, but I've found that for some exercises I had to go even lower, and for some I could lift as much as she did.

I'm taking diligent notes of each workout in a spreadsheet, noting whether the weight I picked was ok or if I should try heavier next time, but even with the same exercise it'll depend on the format of the video - if it's doing it for 45 seconds, or, say going for 10-8-6 repetitions with ascending weight.

And then of course you need to consider that your form may vary from day to day. Sigh... Who knew that weight lifting would be so complicated! :-D

Any tips for selecting the right weight?