I've been invited to the wedding of my boyfriend's sister in October. It'll be the first time I meet any of his family, so I'm incredibly nervous.
I'm very much a jeans and t shirt person, I don't have many dresses, but don't like formal trousers either, so prefer a dress, but I don't like waisted ones, they never sit right on me. Usually I wear T-shirt dresses that are quite clinging, but I have a spare tyre to hide at the moment 
although I'm going to go on a strict diet until October in the hope I can get rid of it. I'm a size 14, sometimes 16 on the chest and waist and have ok legs I guess, large boobs, not much waist. I'm 50, but am told I look about 40 and dress young usually, very informal. I don't wear heels!
Please help me find something to wear! 
My budget is very low, I'm happy to look on Ebay. I need some nice low shoes, flat pumps of some kind too.
Will I have to wear a hat?? I haven't been to a wedding for about 15 years! . I have long curly brown hair and hats really don't suit me. I don't wear my hair up either, it's the natural look all the way! 
I want to feel comfortable, as the whole experience is going to be nerve wracking as it is, so need to be myself if possible! if that makes sense.
Very grateful for any help and advice. I don't really know where to start. In the past I've shopped at Dorothy Perkins, M&S, Next, New Look, Debenhams, Peacocks, M & Co although they are a bit too flowery usually ....
Thank you!