You don't actually need to supply any proof that you have money, properties, etc. Your fiance will be the one to show documents for that, that he can provide for you and accommodate you here in the UK financially. You also don't need to submit NBI, it's not needed. What you need to submit are your passport, birth certificate and Certificate of No Marriage (CENOMAR) to prove that you are free to marry your fiance.

Also, take into consideration that you need to prove that you have a subsisting relationship, so you need to submit documents such as photos of you together (and with family and friends), chat or call logs, gifts/cards from each other if you have, photo of engagement ring if you have, flights and hotel bookings whenever your fiance visits you, etc. These are not requirements stated in the application form but it will be helpful to prove the relationship. What I also find helpful is having proof that you are planning to get married in the UK, like showing some letters/emails/receipts of booking for the wedding, reception, and other things needed.