Now that Marc Miller has passed Traveller to Mongoose I realize he may not be around longer so I should buy what I'm missing from the FFE Store. Looking at the available CDs:

Traveller GURPS 1 - have PDFs from Bundle of Holding
Traveller GURPS 2 - have PDFs from Bundle of Holding
Traveller GURPS 3 - have JTAS Online contents from previous subscription

Classic Traveller - own CD
JTAS - own CD
Traveller Apocrypha-1 - own CD
Traveller Apocrypha-2 - own CD
Traveller Apocrypha-3 - own CD

MegaTraveller - own CD
Traveller: The New Era - own CD
Traveller: The New Era 2 - own CD
Traveller 4 - own CD
Traveller HERO - don't own but other than core books I have supplements converted to other systems
Traveller 20 - own CD

Twilight: 2000 v1 - own CD
Twilight: 2000 v2.2 - own CD
Twilight: 2013 - own CD

2300 AD - don't own
Challenge Magazine #25-77 - own print issues but not PDFs

Dark Conspiracy 1 - don't own
Dark Conspiracy 2 - don't own

With their eternal 443 sale I guess I'd buy:

2300 AD - I like that Challenge had a lot of 2300 AD material so it's a force multiplier.
Dark Conspiracy 1 and 2 - Not really my genre but it's a complete RPG and Challenge also supported this game.
Traveller HERO - I guess for completeness, other choice is Challenge just to have it in PDF format

Hmm not the best web site coding. Adding Dark Conspiracy 2 would always put it in its own shopping cart. Couldn't get around it and didn't want to risk getting the order wrong. In the end I bought just the 2300 AD CD-ROM.