Just as the title suggests what are some tools and apps to increase security and privacy on Android. I’ve seen and used OONI Probe to test blocking of sites and apps on the network and use the duckduckgo browser instead of chrome.
I’m not interested in making it as secure as it can be, as Google will track and trace me regardless so just interested.
If you are on Android 9, you may want to enable Private DNS from advanced network settings. I use dns.quad9.net as the hostname as they are non-profit, support DNSSEC and have a node in Finland.
If you have older Android, but newer than 4.0, and aren’t using a VPN, I would use Intra which is a DNS-over-HTTPS app which sadly isn’t in F-Droid yet. However until everyone and everything supports encrypted SNI, sites you access can be seen through SNI and IP (if there is only one site on that IP), but it protects from DNS hijacking at least.
See also 
Discussion | Firefox eSNI / DoH/TRR #785 .
Do you have any specific kind of apps in mind?
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My recommendation is to first get the Signal APK from their website (Signal >> Signal Android APK) and use it as your default SMS app. Second get F-Droid and turn on the Guardian Project under Repositories to get access to Orbot which will use Tor as a VPN for select apps. From F-Droid also get the Tor Browser and you can set it as your default.