Marth Guide from the Beginning:

Neutral start:

Dash Dance and try to whiff an aerial from the opponent by baiting him, with throwing out quick moves like fair

ur main goal is to get a grab and combo out of it at low percent, thats more like the defensive spacy playstyle

but u can also go for aggressive ones with aerial dtilt approaches, do this moves with the tip of  ur sword and they cant trade u back since u are to far away

DONT USE NAIR, and FSMASH in neutral that often, only use it for mixups, when the enemy is expecting u to fair u do nair

at  mid percent u will try to get them offstage to do an edgeguard, usually u do by doing fair chains, into dair (ken-combo)

or getting a hard read with fsmash

constantly dtilting

tipper ftilt is also very good to get them offstage

easiest edgeguard is to get to the edge (u do this to remove the option that they can go to the ledge, "Sweetspot)

but dont always do this: against spacies when they are above the stage u always want them to get below the stage, so they always have to do upb

usually I do this by running fair, or full hop fair offstage