I can’t hangout

So, my family has been in a tight spot because of financial issues for a while now, but in June, I was fortunate enough to scrape together money for a trip with my friends without any help from my parents. But now that I am back, I am in a bad situation money-wise, and my friends, who I just came back from a month-long trip with in June, want to hang out. Especially because one of them is celebrating their birthday, but I can’t go because I don’t have money to buy them a gift or even go out to eat. My family is in such a bad situation with money that we don’t even have money to buy groceries. I feel so guilty about making up lies to avoid hanging out, but they’re also so persistent. It’s the same four people asking to make five different plans to hang out just in August. One of them wants to travel, even though I just came back from a trip with them. The other hangouts I understand, but as soon as I say I can’t hang out, they want to reschedule instead of hanging out without me.
I feel very blessed to have friends that want to hang out and reschedule when I can’t make it, but at the same time, I feel incredibly guilty, so I keep ignoring their texts instead. I don’t know about telling them because even though I told one of the girls who is planning the trip, she is still counting on me going and asking if I can scrape together money to go. It feels incredibly weird to tell the birthday girl that even though she spent money on my birthday, I can’t give her a gift or come to hang out because of financial issues. Now I just feel frustrated because I’ve been trying to tell them I am busy and that this month is a bad time, but they just keep on rescheduling and stuff.
I am low-key feeling resentful as well because why are you forcing me to spill my hardships instead of just hanging out yourselves? I just came back from a month-long trip with you all, and I have met almost all of them once after that as well. I get that they want to have fun and hang out, but I can’t be there, so go without me. I am perfectly okay with that, but they won’t. It feels like a lot of friendships in the group can’t work without me, but I hate that thought and responsibility if that is true.