My tips for planning, don't bother so far in advance. Buy the charts, decide where you want to go and via and then just plan a leg at a time as you go.
I did an experiment last summer to prove how little you need to worry about advance planning when crossing Europe. I flew to Guernsey-Clermont Ferrand-Nice-Milan-Cannes-Dijon-LFAT over a long weekend and only decided on the next leg while refueling from the first.
It's no difficult, just get your weather, NOTAM etc as you and enjoy the freedom.