So I'd maybe start by seeing who you can rule out in your area? So for example in your constituency you have two parties that have very strong and prominent policies relating to Scottish independence (for/against) so I would imagine that a lot of Scottish people would immediately rule out SNP if they were strongly against independence, for example. Here in England, I might automatically rule out the party that is known for particularly extreme right wing views without further investigation.
After that, I'd maybe think about one or two issues you feel particularly strongly about and then you could read the relevant parts of the manifestos of the remaining parties. For me, my priorities are education and trans rights so that's what I would seek out first.
Some people think about tactical voting and you can have a look at
this website to see what the current predictions are to see if you might prefer to vote for your second instead of first choice in order to try to keep out a party you really dislike.
If you have a TV license, the BBC has lots of shows relating to the election- Question Time very often has a representative from the SNP as well as the main GB parties (Labour, Conservative etc). There was one episode filmed in Edinburgh I believe which was Scotland specific that might be interesting to watch to see the parties being questioned about their policies.
I hope some of that is vaguely helpful and I've not been too intense!