Oils and fats are on the fourth level of the vegan food pyramid. You should have 2-4 tablespoons per day, of which at least 1 should be of an oil that is high in omega-3 fatty acids such as linseed oil, rapeseed oil, walnut oil, chia oil or hempseed oil, perhaps enriched with DHA and EPA (alternatively, use a supplement based on algae, either algae oil or algae oil capsules).
Spreadable fats (vegan margarine/vegan butter) these days are no relevant source of trans fatty acids anymore, so don't worry – eating them won't do you any harm in this respect. However, consider that certain oils, such as sunflower oil and safflower oil are very high in omega-6 fatty acids. Do not eat too much of them, including sunflower or safflower margarine.
Apart from that, prefer little processed oils. For cold dishes such as salads, pick native cold-pressed oils. For frying or baking, prefer oils that tolerate high temperatures such as rapeseed oil (refined for very high temperatures).
