If it's something they'd get rid of anyway (old gadgets, furniture, dishes, whatever), I think it's ok to take it off their hands without feeling like you're mooching.
If it's something that has significant resale value, e.g. phone, computer, car, then offer to pay them a reasonable sum. Depending on your family dynamics, they may refuse (mine would). But it at least gives them a chance to get their money back.
As far as going out, I think this is a case of frugal vs cheap. If you can't afford to go out (debt emergency), refuse stoically. But if you can make a little room in your finances, and can't bring your friends around to your ways of thinking immediately, and are unwilling to give them up (as I would hope you are, if they are friends!) then I think it's reasonable to simply scale back; e.g. go out with them once a week for one appetizer-as-entree and one drink. From what I gather as a newbie, mustachianism isn't necessarily about hard rules (e.g. NEVER eat out, etc), it's about optimizing decisions for max happiness, while knowing that consumerism does not bring true happiness. Friends and family do, however.
Goes without saying, keep trying to involve them in non-consumer activities.