marmot115:

It sounds like a Visit Europe pass [need to fly a OW carrier to Europe and buy this off the back of it] might suit your needs for the European legs. For the full itin I suggest a RTW ticket [eg OW Explorer].

As well as providing an idea of where you want to go so others can help you, keep in mind these general rules:

Max stopovers per continent [except that of origin] is 4 (6 for the US)

A stopover is classed as being in the same place for > 24 hours

Each journey is not necessarily where you're coming from and going to, but based on number of sectors or hops from where you departed to where you'll end up using OW carriers - so, for example, LHR-SFO using a combination of BA LHR-JFK, AA JFK-SFO would be classed as 2 sectors.

Many OW airlines operate codeshares, but the rules governing whether you can use them more often than not state you can't.

Many of the regular posters on this board will be happy to help guide you on your way; go get a travel agent to help you plan a basic itin then get the real experts to help

Best of luck with your first RTW - beware, once done they can prove very addictive!