I also would like to point out you have lots of solos in the current set you posted.
If you plan on playing a specific combo, you'll want to increase the chances of it occurring by repeating cards. For example, your Ob Nixilis, Mohamoti Djinn, your Radiant Fountain are solos that I would personally remove to add other cards that are part of the strategy.
This is great advice!
I would also suggest that Master of the Feast is a violation of this as well. I would suggest replacing these with cards that synergize with your overall strategy better. Perhaps 2-3 Heliod's Pilgrim? It would almost add extra Ensoul Artifacts, and would add tons of value to the 1-ofs Singing Bell Strike and Ephara's Enlightenment.
I would also consider moving Erase and Solemn Offering to the sideboard, since they can be completely dead cards in your hand for some games.
Congregate is a card that's easy to fall prey to. It looks like a great card to have, until you start to play with it and notice that one of three things usually happens: either a) You cast it for a ton of life because you have a ton of creatures on the field, so you win with a ton of life (you would have won anyway); b) You cast it and gain a ton of life because your opponent has a ton of creatures on the field, then you lose because your opponent keeps attacking you (you would have lost anyway); c) There aren't many creatures on the field and nothing really changes. There's very few cases where a card that costs 4 mana and doesn't do anything to change the board state is better than another 4-drop that does impact the board. Consider replacing these with something that saves you life (like Murderous Cut) by impacting the board.
My last piece of advice would be to tweak your lands a bit. At least the 1-of Radiant Fountain should probably be replaced with fetchlands (Evolving Wilds is a good budget choice here). Whenever you're running 3 colors on a budget, it's important to pick ONE to be your most important color (appears to be blue here) and splash into the other colors lightly. This will allow you to run more basic Islands (for early 'comes into play untapped' sources), and raises the chances that you'll have your other colors by the time you need them (hopefully not until turn 4+). Stay away from any double/triple symbol costs that are in your splash colors (like Master of the Feast) unless they have a good chance of just winning the game themselves (like Elspeth, Sun's Champion).
I hope something in here helps!