Create own package repo for an offline Ubuntu machine

I have some offline Ubuntu 18.04 LTS amd64 machines for sw development and I need to create a package repository for them. (or in worst case a directory containing the packages). How can I solve this? I need a collection of common c++ and python related packages (standard c++ libs, pip, numpy, ...) with all dependencies. Appreciate every answer Edit: the point is how to get the packages on another (type of) system.