I consider every RPG to be a toolkit, and T5 is one of the most comprehensive toolkits I've ever used. However, it's not for the faint-of-heart. You have to really want to run a T5 game to do it, and it's best if you're familiar with some other edition of Traveller. It also helps if you and your players don't mind a bit of handwavery in lieu specific implementations of rules -- melee combat, personal interactions, and vehicle chases, for instance. I have some short-cuts for these that I use, and I roll flux a lot. I don't like to get bogged down by complex rule executions and don't feel obligated to follow any rulebook to the letter. That said, I do my best to understand a rule before I handwave it.
I started my first T5 game when it was still in pre-release, and I ported it from Mongoose Traveller (pocket edition, still the best modern implementation, IMO). My second game I started after I got my BBB from the Kickstarter and I've been running it ever since. We meet every other Saturday. It's a lot of fun and I look forward to my sessions.
All told, counting the Beta game and the MgT game, I had about 3 years of prep, playtesting, and picaresque game sessions before I launched my current campaign. I wrote some software tools to help with MTU generation and added some of my own data and derived-data. I built several of my own starships from specs from other Traveller editions, like the Yacht Type-Y and the Scout/Courier Type-S. I used RObject's tools for a lot of stuff until they went away. Heldenhaufen.de/T5 had some good stuff, too, but I don't think it's there anymore either. The Traveller Wiki will help a lot with adding depth and color to your Traveller game. It has helped a lot with mine.
Two things stand out to me as lessons learned in all this. First, I should have read E.C. Tubb's Dumarest of Earth books sooner. If you haven't read any of them, go do that right now. Second, I left MgT behind because there wasn't enough depth for a long-term game, IMO. T5 with it's toolkit approach to defining the game was a significant leap -- maybe too significant, but I've never been one to shy away from a challenge of that nature.
My advice for newcomers to Traveller is run a picareque game using MgT or the LBBs. Lay out your adventure, roll up the characters and run 3-5 sessions. If you want more -- and I'm refering to stuff like transhumanism, alien species creation, and making your own stuff (vehicles, starships, guns, armor, gear, etc.) port in rules from T5 as-needed. They're mostly compatible with a bit of Handwavium to mortar the gaps.
That's more than I've written in a while. I hope someone finds it helpful.