Starting studying again
At least with the Pali suttas, start with the first three sermons: 


https://suttacentral.net/sn56.11/en/bodhi + https://suttacentral.net/sn45.8/en/bodhi
https://www.accesstoinsight.org/tipitaka/sn/sn22/sn22.059.mend.html
https://suttacentral.net/sn35.28/en/bodhi


Then basic moral teachings, such as: 


https://suttacentral.net/mn61/en/horner
https://suttacentral.net/sn55.7/en/sujato
https://www.accesstoinsight.org/tipitaka/dn/dn.31.0.nara.html
https://www.accesstoinsight.org/tipitaka/kn/snp/snp.1.08.amar.html


In the Buddha's Words An Anthology of Discourses from the Pali Canon by Bhikkhu Bodhi is a good compilation (although take care with Bhikkhu Bodhi's often sectarian footnotes).