For the average person, almost any food can increase their weight if consumed in excessive amounts. Almonds happen to be high in omega-6 so I wouldn't concentrate on that alone. I think it would be better to eat a well balanced healthy diet and increase your calories from all sources.
Here are some ideas.
Walnuts (high in omega-3)
Avocado (contains healthy oils)
For example, you could make a big salad (fill up a big salad bowl) and include chunks of avocado and walnuts. (Eating just avocado or walnuts alone is not a good idea.) Also, for protein, you could add chicken or eat some fish separately. You could also add a couple teaspoons of olive oil to your salad.