I tried installing a modded playstore using Lucky Patcher but in the process it deleted the system app and didn't install the modded one. i have tried installing it manually but it just can't work and crashes every time i want to download or update apps. can anyone help me out?
Just flash a GAPPS package available on xda. You can choose from a variety of packages, available on multiple versions of Android. See here for more information.
Install the playstore. Then convert it to system app then reboot. Thats all. To convert, you can simply use ES file explorer. With this option first uninstall the play store. Enable root explorer in the app dashboard. Still in the dashboard, tap local and select device. Look for system, app and there paste the playstore apk file there that you have copied ( so you first copy the playstore apk before going to root explorer). Next reboot.
Or you can convert to system app using any root app like Link2SD. Here u need to install the playstore app, next you open Link2SD and select playstore. Tap the more options button and tap convert to system app. After it is complete reboot
The "Install Modded Play Store" dialog in Lucky Patcher also supports installing the unmodded Google Play store. To do this, open Lucky Patcher > Tools > Install modded Play Store > Original Play Store (select version). Make sure to uncheck "Install as a User App" before installing. Then reboot.
If it doesn't install right (or doesn't appear after reboot), you could try it manually. Go to Rebuild & Install > LuckyPatcher > Download, select PlayStore.apk (which was downloaded by installing the unmodded Play Store above), press "Install as a System App", and then reboot.