How can I most effectivly secure and anonymize my specfic Android device?
Hi the best place you are probably best off looking is the XDA forums for advice on the routing part. 

Also have a look at microG, a project that is attempting to replace google play services and make android truly open source.  Heres a link to an article that covers MicroG

Geolocation would be difficult to anonomise I'm guessing due to  triangulation techniques that could be used to track the device location through the mobile network.

Good antivirus and malware software is a must

Alternative app stores such as F-droid, XDA, ect would be a good option - remember that apps can contain trackers ect which can send your data to the developer. Maby try and find an app that shows these permissions?

Signal - good private messaging replacement 

Remember, to be most secure you will need to update regularly and also rooting your phone can mean the latest security patches are not rolled out as fast, if at all.

Edit: I forgot to add that if you do add a custom ROM, makesure that you encript your device :)