So sorry to hear about your dad.
Hire a local hall (village hall, community centre, rugby club etc, depending on what you've got in your area).
Instead of a present, ask guests to bring a bottle of wine and a plate of food for the buffet. I think most people would be fine with this, I know I certainly would.
For the cake, do a tower of store bought cakes - fondant fancies, jam tarts, etc.
Dress - preloved.
Flowers - ask a friend to sort, or do them yourself.
Do some DIY decorations yourself, or have a hen night of making decorations, practising makeup, trying out hairstyles, getting in a takeaway, and having pamper evening.
Car - if you know anyone who has a decent car, ask if they'll drive you for a donation to charity.
Photos - just ask friends and family to take lots of photos and send them to you after - you can make up some albums yourself.
Suits for men - ask them to wear one they already have, or hire them
Bridesmaids - preloved, or ask them if they would mind buying their own, or wear something suitable they already have - just go multicoloured, rather than have a set colour, so they have more choice about what to wear.
DJ/music - borrow or hire a sound system, or decent speakers. Or splurge for a DJ, depending on cost, if you want a full disco/party in the evening.
Hire some plates/glasses/cutlery if you need to, or just stick to paper plates etc.
I hope you make some lovely memories xx