Not perfection. Not centring the child at all times. It's more a balancing of needs so that everyone gets their basic needs met, including mum. Understanding that in order to meet basic needs sometimes different people (including yourself) need to be prioritised, and sometimes only the basics will get done, that's OK.
Meeting physical needs: Provide regular food, of a type which is not going to harm them (e.g. so much sugar their teeth fall out, or so much junk they are overweight by 2, or so much salt their kidneys are overloaded) but other than this, does not need to be perfect nutrition. Ensure they have a place to live, sleep, play, which is free of hazards (including not disgustingly dirty) and has space for them. Wash them/get them to wash and provide clean laundry, regularly enough to avoid irritation of the skin from dirt or unpleasant smells (in puberty - as much as you can reasonably avoid these).
Protect them from harm as far as possible - keep them away from drugs, violence, adult/sexual stuff, danger. Don't leave them to navigate dangerous things until they are capable. Deal with situations that you know are causing them harm. (As far as it's in your control). When you're angry with them or they have misbehaved be reasonable. (Showing anger is fine, showing aggression not.) If you snap, apologise and move on (maybe seek better coping strategies, if it's a recurring thing) rather than blaming them.
Care about them, love them, be interested in them (nb not necessarily interested in every single interest that they have), show them physical affection, take them seriously, and see them as an individual. But don't treat them like the centre of the universe. You don't need to make them happy all the time or prevent them from ever experiencing anything hard, you need to love them through the happy days, the sad days and the angry days. The easy days, the hard days and the impossible ones.
Show up. Just be present and don't leave, or be in and out of their lives. Be a constant presence for them, be stable in yourself. If you're struggling, get help rather than self medicating or partaking in risky behaviour etc. Be a responsible adult, provide the basics (Food, shelter, heat, security) financially before anything else.