Avoid purchasing materials that are too cheap as they are usually not flattering or will not last. You can see some properties of textiles here. Best to get only the clothes that you love and that have a chance of lasting.
Don’t mix a tight skirt or jeans with a fitted top. Aim to have either a fitted skirt with a loser top or vice versa. See also my suggestions on ways to wear leggings over 50.
Virtually nothing is more crucial than dressing in a way that satisfies and stands for you. If you know your style and know your body you can break all of the rules or add items from the ‘don’t list’ as you please. My find your style obstacle will assist with that.