Stay clear of purchasing fabrics that are too inexpensive as they are usually not flattering or will not last. You can see some characteristics of textiles here. Best to get only the clothes that you love and that have a chance of lasting.
Don't mix a fitted dress or slacks with a tight top. Aim to have either a tight skirt with a loser top or vice versa. See also my tips on ways to wear leggings over 60.