Since this deck is meant for casual play I'll not go into the strengths/weaknesses of the deck.
Purely based on the number of lands you have in your deck I'd suggest to cut all cards that cost 5 CMC and more except for
Daybreak Chimera and
Sephara, Sky's Blade as they have alternative casting costs.
With 20 land your 5+cmc cards are going to be sitting in your hand most of the time.
In a basic deck like this, (without tutors or ramp etc ), with 20 lands / 60 cards, you get on average 1 land for every 3 cards you draw.
That means, for example, you'll need on average 18 cards = 11 turns to get to 6 mana before you can play a
Serra's Guardian.
A lot of games will be over by then.
To give your deck a better
fighting chance, I suggest :
Up your land total to about 22
Add at least 6 1cc creatures
Round out with more 2cc creatures.
You'll notice your deck is more on curve and you'll be able to play more spells as opposed to having cards stuck in your hand.
As a general rule of thumb for beginner's deckbuilding start with this type of build :
- 24 land
- 12 1CC
- 12 2CC
- 8 3CC
- 4 4CC
Good luck.