For a sustainable future as a vegan, learn continue to develop your beans and lentils repertoire of recipes. There is lots of protein in these beans. They are low fat, filling and if you explore the cuisine well you will find plenty that tasty. I recently learnt from a vegan that its not necessary to pair the beans for whole proteins. when you understand what's involved, it makes sense. Mostly what's missing in any one food is just a part of one protein and you might get that from a vegetable or some other thing you are eating but for the sake of taste and satisfaction these pairings are well worthwhile.
I would start with learning indian recipes.
There are also some great italian and greek bean soups though they usually include meat for flavour but its still possible to make tasty dishes without the meat base flavours.
lean how to make hummus.
mexican frijole. of course the mexicans and south americans have lots of bean dishes.
go to cooking classes if you need a bit of motivation and excitement.
go and try the bean dishes in indian restaurants another restaurants for ideas. Try to analyse the recipes.
learn how to cook iwht spices.
Actually indian bean dishes can be surprisingly simple with only a about three spices but if you don't mind hot food, you can even buy boxes of spice mix.
baked beans on toast is an old favourite of mine too.
All beans and legumes are very healthy and nutritious. Probably one of the best whole foods around.
also includes seeds on your salads or a few nuts. These make your salads really tasty and in order to help you from blowing your diet on nuts putting them in a recipe is a great way to use them.
I think you could easily eat more lentils and beans without blowing your calorie intake. I"d go for a cup a day at least.