Important things about using Seasons Past:
Always return as many Fogs as possible (can't be more than three, though), and don't forget to also recurr Evolving Wilds as your cmc 0 card. And never forget to recurr either Final Parting, Mastermind's Acquisition or Dark Petition. The game is basically over if you forget that (unless you already have a copy in hand). It isn't always easy to decide between your cmc 4 spells, but as you usually want the board to be as clear as possible, Settle the Wreckage is a great choice in most situations. If your opponent relies on planeswalkers a lot, Vraska's Contempt should be the weapon of choice. Casting multiple Lost Legacy per game can already be game winning against combo or control opponents, as the first cast usually gives you a good idea what their deck is about, so picking it apart is no problem from there on.
Nissa's Renewal looks super weird, but having access to it makes your Seasons Past cycles a lot more impressive. It ramps you towards the 14+ mana you want while giving you 7 life. Against some opponents, that is a damage output of three or more turns, and even against ramp or burn, you gain at least one additional turn.
Wilderness Reclamation is another incredible card for the deck. Where we had to wait to cast a tutor before, we can now cast a turn 4 reclamation, untap and fog, and can cast a tutor on curve while still having defenses up.
Although the deck is three coloured, it does play 15 basics. This is because you want to abuse both Evolving Wilds and Nissa's Renewal as much as possible. It isn't that problematic as well, as most of your spells don't have any fancy mana costs. A great side effect of this is that the deck is pretty cheap to build. Always a good thing in my opinion.
The latest addition is one copy of Veil of Summer. This is a great tutor target when we need it, but won't come up too often in games where we don't. It's great when a powerful card that fixes a deck's biggest weakness is released and even has a name that's on flavour (because, as you might know, summer is a season).