For mages, I like Kukulkan, Ra, and Anubis for new players. They are not very mechanically complex, and have abilities that are not too difficult to use effectively!

All gods can be built for damage or bruiser (a mix of damage and defense) but typically mages and carries are the most likely choice for full damage. If you are just starting out then I would suggest trying mages with easier to hit abilities at first and less skill shots, gods like discordia, kukulkan, poseidon, scyla, and maybe even the newest god ix chel. All of these have fairly easy abilities to hit and good wave clear (very important in conquest). A standard build for best damage is a mixture of cooldown, early game flat penetration, and then late game percent penetration to help with tanks as their tank items come online. Try starting sands of time > spear of desolation > Devine ruin (especially if they have healing) > rod of Tahuti > Charons coin/obsidian shard > soul reaver. Late game you will upgrade your sands of time starter into pendulum of ages. This is a very standard build and can be altered if no anti heal (Devine ruin) is needed in cases where the enemy team has no team healers like yemoja, horus, guan yu, aphrodite, etc… Gl and have fun.