If you properly flash the latest CM12.1 (20160110-Nightly) and properly flashed the Gapps package. And as soon as you boot up the phone you get all these app crashes and some apps are not working here is what you do:
First: download ES File Explorer
Second: using es file explorer navigate to your sd card and find the gapps zip file that you tried to flash and open the zip file, next open the system folder.
Third: now you must open each folder and check to see if it has an apk file and download and install it too your phone
*don't worry if it doesn't show new permissions before instillation or if apps are still crashing while your do this cause after everything has installed the crashes should stop*
and the gapps package that i am using is (gapps-5.1-2015-04-20-15-56-24) if you want to be sure that it works
oh yeah and make sure you thanks me I helped