OK, I'm worried that my art might be suffering from same-face syndrome, and people have suggested that I draw more faces from life, but I have a few problems: 1. How do I know the ethnicity of the person whose face I'm sketching? What if they are mixed or are from a more uncommon ethnicity, such as Lebanese? 2. How do I know which types of facial features to use for any character?
You don’t need to know specifically the ethnicity of the people you’re drawing. Researching different cultures of people is a great way to expand the types of facial structures to draw, but unless the character is super-specific, I doubt many people will quiz you on that character’s heritage based on their facial appearance. Just concentrate on drawing different shapes in the face.
Buuut if you really want to study facial structures of different ethnic people, either google it, or check out this handy guide.
so i'm currently trying to learn perspective, but all the drawings i make of blocks, boxes, etc. are always looking distorted/warped. is there any tutorial or something that could help me with this?
It sounds like you have your vanishing points too close together, which causes the warped look. A good rule of thumb is to atleast have one vanishing point out of the field of view (the picture).
There are tons of perspective books cheap that I highly recommend reading, but you can start out with Fox-orian’s tutorial.