Parts list for irrigation system

OP, i think you’re getting the drift.
While this may be a project based on an Arduino processor, there are multiple separate ‘projects’ that need to work reliably by themselves - before they can be combined into a reliable, working ‘system’.

We all started like this - and we have cupboards / drawers of stuff we bought that was unsuitable for the project at the time.

You and your husband can do it, but it will take patience and perseverance!