How can you be a kind, giving person without being taken advantage of?
There are three thoughts I have on this, based on observations of how Jesus dealt with people in the Gospels.
1. Learn to differentiate between people who are in need and people who are needy, demanding, or manipulative. There are people who are genuinely in need. Jesus helped those people. But then there are people who are users. There are people who enjoy getting their way and getting others to give-in. And there are some people who are manipulative and don't even know it -self-absorbed and adept at denial, blame-shifting, and finding people to affirm them and tell them how wonderful they are that.
2. Learn to identify what the real need is. The real need is not always what the other person advertises for. Even in the case of a needy or demanding or manipulative person, their real need is obviously not that you acquiesce to their whims. It may be that you say "No" to them while still showing them kindness and respect.
3. Pick your battles. While it is certainly right to stand up to people who want to take advantage of you, sometimes it isn't a battle worth fighting and placating them is the quickest way to get away from them, which is what you really want. This is hard for people who make being taken advantage of a matter of their own ego, but if you can pick your battles with wisdom and accept that some people are just going to take a bite out of you (and that the effort of trying to stop them or seek justice may not be worth it), you will be freer.