Hi Robert,
Welcome to the wonderful world of 7mm. Moving up from 4mm will immediately give you the pleasure of having rolling stock that has 'weight' and inertia. The way even just a wagon trundles over pointwork is a joy...anyway my pennyworth is to buy a couple of Slaters plastic wagon kits and a yard or two of flexi track. No need for a soldering iron but will give satisfaction in a short space of time and will build confidence rapidly. Slaters kits are easy to put together as is, but can be upgraded with more detail if you wish.
Best,
Richard