So this is a mostly Budget control deck for the Gladiator format. 

90% of this list is from the starter decks containing either [R] [U] or [W] (there's 10 decks the game gives to you with singles that could go in this list). Anything else is draft chaff Ominous Seas , or something I opened in a pack Narset of the Ancient Way (Narset is 100% replaceable, she is just there because I happened to open her). 

The gameplan is very straitforward: You're trying to survive the early game, until you can drop one of the bombs in the deck that cares about drawing cards or casting non-creature spells, both of those serve the same purpose, if you can resolve a bomb and survive until your next main phase with that bomb on the field, you should be good to go. Bombs in this deck include: Niv-Mizzet, Parun Thousand-Year Storm Shark Typhoon there are some non-six-mana bombs as well Ominous Seas and Whirlwind of Thought are both going to serve that bomb role as well. 

Once one of those is in play, feel free to go off with Inspired Ultimatum hard cast Boon of the Wish-Giver, Mission Briefing back your Commence the Endgame etc. 

Don't worry too much about running out of card draw in the early game, but it can definitely become a problem, since Arena has a lot less power available in the "Do a thing and draw a card" department than traditional magic, so most of your card draw is centered in big bursts, which can be tense and polarizing. Hopefully resolving either League Guildmage or Spectral Sailor will help add some consistency. Because you're trying to do almost everything in this deck at instant speed, you'll often have the pleasure of holding up something like Essence Scatter, not having a target on their turn, and having mana open on their endstep to draw some cards off of permanents you control. 

Your creatures like Sprite Dragon Wee Dragonauts and Fire Urchin are mainly there to clog up the board/block for you, but sometimes opponents will blow valuable removal on them, which helps your Niv-Mizzets and your other bombs not walk right into removal. Sometimes you'll just get a win off of Wee Dragonauts + Raking Claws getting in when they don't expect it. 

This is a budget/F2P list, I'm sure there are improvements that could be made, and I'll definitely be tweaking it as I play more matches.