The standard rotation that pretty much all mdks use with little variation is:

eruption, rearming trap, flames of oblivion, bar swap
engulfing flames, burning embers, blockade
5x whips
engulfing flames, burning embers, blockade
1x whip, bar swap
repeat

Light attack between each ability, use standard of might on the back bar when it's available.

The standard mdk bars are:
flame lash, engulfing flames, burning embers, inner light, blockade of fire, shooting star
eruption, rearming trap, flames of oblivion, inner light, harness magicka, standard of might

Replace inner light on the back bar with molten armaments if you're too cheap to use spell power pots.

Gold out your weapons and enchants. Everything else is OK purple.

All attribute points into magicka. Use cp150 health+magicka food.

Lookup mdk guides on tamerialfoundry for CP suggestions. NOS's guides are usually good.