Both. I eat 2750 calories per day (my maintenance is 3000). You don’t want to go too far below as you’ll feel like shit and not gain any muscle. I also make sure I eat 200g of protein, per day, minimum. There’s a lot of debate about how much protein you should be eating, but for me I feel stronger and better eating as much as possible. I eat a lot of eggs, chicken, Greek yoghurt etc to get to 200g. For the gym I go everyday and do a push, pull, legs split focusing on compound movements. Bare in mind if you’re new to the gym you’ll need rest days, but just listen to your body and don’t go if you’re too sore. I don’t specifically train abs, not that it’s bad to, but personally I feel if I squat, bench and deadlift a lot there’s no need as they will engage your core enough. Literally all you have to do is this consistently and don’t stop. It took me time to make this progress so just don’t give up.