Cheapest way to travel to zone 1?

Hi, I am absolutely freaking confused about the train systems, oysters, tapping in out, travelcards. I'll need to travel to Euston Square station, NOT London Euston, which is in zone 1. This will be my daily uni route.I'm gonna take the Hammersmith and city from West HamI'll be travelling from South Ockendon, which isn't an area for travelcards. I thought I could get a travelcard for zones 1-6 and just tap that way with an 18 student oyster. But apparently the start station isn't in a zone, and also apparently I need to be a resident of london to be eligible for the oyster?So I feel like I'm a little bit screwed because idk what to do?Do I buy a ticket daily, in South Ockendon until West ham, and then use my debit card to tap in at West ham and out at Euston Square?I'm so freaking baffed.Could anyone please please please, tell me what the cheapest way to travel would be, and how much it would cost me? Ideally I'd like to be paying monthly but I'd honestly appreciate any helpThanks