I've used silica gel for years to preserve flowers. You can use it over and over by drying it in a low oven before starting a new batch of flowers.
Some flowers retain their color better than others. I would google how to use this method for best results. It's trial and error but if you enjoy doing it, it's a lot of fun and you get better with practice.
Another nice way (but the results look different) is hanging flowers to dry. Again, some turn out better than others.