I honestly don’t think that composite build ups on your front teeth are the answer. As you are wanting to create the illusion of the gap being closed, then your front teeth will look ridiculously wide.
The same problem you would have with veneers. To close the gap, the veneers would have to be alot wider. This may mean that you have to have more teeth veneered to create the best symmetrical appearance. Hope this makes sense.
I think that orthodontics to close the gap may be your best option. There are lots of different appliances on the market that work really quickly- and some are quite discreet, so don’t dismiss the idea totally. Good luck