Here's my opinion on Vanadium setup.
A lot of people like to use other browsers like Brave on GrapheneOS because Vanadium doesn't have fingerprint randomization. However, the fact that all GrapheneOS phones run on the same Pixel phones means that it is difficult to distinguish two different Vanadium users. Thus there is an argument that Vanadium is actually better at preventing fingerprinting than randomization.
To make Vanadium fingerprinting protection better, try to keep settings close to their defaults. Instead of rejecting cookies, which can break sites, use incognito mode to clear cookies after each session.
You can also use bookmark icons on your home screen to add convenience. You can make a launcher icon that opens a new incognito tab so that you don't have to do it manually every time.
For ad blocking, the best way is to either use a DNS blocking tool like Pihole, a custom DNS server or to use a VPN that has ad blocking built in. This will also block ads in any other apps you use. https://grapheneos.org/faq#ad-blocking