Since there are so many banners to summon from, it can get very confusing which one to pull. Below summarises the "cheapest" way to pity Squall.

1. 4k vis - 80 mindsperes banner x 2 (200 medals, 160 mindspheres)
2. 11k vis - 3 steps on Step-Up Squall banner x 2 (600 medals, 80 shards)
3. 8k vis - 6 steps on 9-step Rinoa banner (600 medals, 1 blossom extras)
4. 12k vis - 6 steps on Squall pity banner (600 medals)

Cost: 35k free Vis

Outcome: 2000 medals (pity Squall), 80 shards, 160 mindspheres, 1 blossom extras

The caveat is this does not give you the highest chance to pull Squall before pity, but it's not like most of us aren't going to pity him whichever way we choose.. so might as well go the cheapest route. And if you pull Squall before pity, hey you still have all the shards/mindspheres AND medals to use!

Of course if you use paid vis, you can substitute any of the above step with the paid vis banner instead.

Note: Squall is on Rinoa's 9-step banner with no rate up (0.02746%). You could opt to do all 9-steps on Rinoa banner to get the goodies if you want (in exchange for lower pull rates). Or skip Rinoa's banner altogether for 4k more total Vis cost to have a higher chance at pulling Squall.