The single player will help you learn the mechanics of the game but won't train you for multiplayer.
So your goal for now should be to learn the equipment, citadel upgrades and 1 demigod.
I would recommend learning (pick one) beast, oak or erebus. Play that one demigod a lot until you are comfortable with it.
There are multiple guides in the strategy section, read the guides for build strategies. (I recommend staying away from minion builds for oak/erebus for now)
Save your favor points until you can get blood of the fallen (BoF)
Recommended "universal" basic gear - you can wear more than 1 piece of the same gear (ie. two pairs of boots, two helms etc.)
Banded Armor
Scaled Helm
Unbreakable boots
Vlemish Faceguard
Plenor battlecrown (only really useful if you have scaled helm or vlemish faceguard equipped)
Nimoths Chestpiece
Narmoths Ring
Citadel upgrades: (these need to be purchased in every game)
Fortify structure 1 (asap)
Currency 1 (right when you hit warrank 3 - 1620 war score)
Once you reach war rank 8 you can get creeps: Priests, angels, catapultsari (your team needs to wait to purchase all 3 of these until the team has the gold to purchase all 3 at once - in most situations)
Then at warrank 10 - giants
(it is also beneficial to upgrade armor + attack for creeps)
Ignore most of the other citadel upgrades.(at least for now)
Best consumable items (please keep in mind that consummables are a 1 time use so dont go overboard in purchasing them. I don't recommend health / mana pots)
Teleport scrolls - always try to keep 1 on you - only use when necessary
Flag locks
Sigils - these are a game staple. Learn how to use them (usually towards the end of the fight in an effort to either stay alive or get enough health to take out your opponent) - in online games expect your opponent to have one of these.
that should get you started bro !
j