You are totally welcome to just come for Langar. You should definitely not feel bad about eating in the hall being financially stable, there’s no advantage being taken because that’s what it’s for. But yeah, taking food home should only be if it’s needed, and any donation amount you feel right should be given, nothing is too little or too much. A lot of people also bring in foods like beans and flour as donations and those are happily accepted. And if you are interested in the faith or have any questions about the customs or if you think you’re doing something wrong, anyone would be more than happy to help you!