To answer your question...yes I think it is completely inappropriate. If you want gifts, have a friend throw you a shower.
Engagement parties are not held for gifts...they are for announcing your engagement and intentions to marry. A celebration. Not a shower.
Please don't take this as a personal attack...as I certainly do not mean it to be that. If you cannot afford the wedding you want, change your plans to either something you can afford, or take out a small loan to pay for it...however I do not necessarily condone creating a large debt for a wedding. Weddings can be beautiful without costing a fortune and reducing everyone to poverty. Don't expect monetary gifts from your guests to pay for your wedding.
I have seen your DIY posts and they are great...keep up the good work. Your wedding will be beautiful.