Hello.. you should ideally be going through your country specific guide on CIC webiste to understand how to proove your relationship.. each country has a set of guide on what docs to provide in the application.. Dont miss out on ANYTHING from that.
Additionally, you can provide them skype/whatsapp/viber chats, call logs, pre and post wedding, engagement/weddings pics, social media checkins and posts/photos, financial assistance you may provide to your wife.. gifts which you guys might have couriered or exchanged.. honeymoon bookings, wedding venue bookings etc if any... This kind of stuff helps prove genuinity.
Also some one told us that its best to submit your docs 1-2 months after your wedding so that you have adequate proof of relationship after marriage in terms of skype,chats call logs etc
Hope this was of some help.
Best wishes for your upcoming wedding.