For those of you who need Android 8.0/8.1 Gapps, you can use these Gapps here. These gapps are “minimal” and give you just the Play Store for any Android custom ROMs based on Android 8.0 or 8.1 Gapps. These Android 8.0/8.1 Gapps are 100% compatible with custom ROMs like Resurrection Remix ROM v6.0 (which is based on Oreo) and many others.
Download Android 8.0 Gapps – Link
If for some reason, the above Gapps don’t work, try this – Link