I've made a bunch of mods, but I'm not quite finished yet. There's still suspension work to be done. But if you're just doing summer road touring, I'll stick to the things I think will be of the best benefit to you.
First, you should get a good feel for your comfort on the bike over long periods of time. Are your arms cramped? Back hurt? Knees feeling some strain? Take one day to make a 450+ mile trip and you'll start to see where you and the bike are not fitting. If you feel that your legs are cramped, there are two solutions: 1) get a thicker seat -- the stocker is quite low compared to some of the other Triumph or aftermarket options (I have the solo seat + rack) 2) get a peg lowering kit. If you want something
relatively minor, try the Vario footpeg set (25mm/1" drop). If you need something more extreme, I highly recommend modre's peg lowering kit (2" drop).
Also, consider bar risers or a different pair of handlebars if you are having arm/back problems. It's really quite cheap and relatively easy to swap them out. Just make sure to coordinate with your wind protection choice, as you can put yourself back up into "dirty" air before you know it.
You will almost assuredly need some form of wind protection. You can go big and effective with something like the Parabellum, or you can stick with something smaller. I used to have a Parabellum, but I couldn't take the look after a while. I now use an MRA Roadshield, which does a good job at keeping the wind off of my chest but isn't as effective as the giants. It saves a lot of fatigue, which is what matters most.
I would also suggest investing in a throttle rocker and bar end weights of some sort. I'm a cheap bastard at times (despite how much I've spend on the bike!), so I filled the ends of my grips with washers. You may have better results with "real" bar end weights.
Okay, so that's the (relatively) cheap stuff. If you are comfortable, you can ride longer and more safely. If you have not upgraded your suspension, you may also wish to do that. It may be expensive, but it makes the bike much more tolerable (and safer) over a long period of riding.
If you are looking for luggage options, you have options ranging from "kinda" expensive to very expensive. RedBird has a nice soft luggage setup. Between the tank bag, seat bag, a panniers, you can hold a lot of stuff. If you're looking for something tougher and waterproof, check out Wolfman Luggage's Expedition rear bags (they also make tank bags and soft panniers). It's the yellow bag in the picture below. That one is the "small", which holds my tent, sleeping bag, bivy sack, sleeping bag mat, compression pillow, jacket/pants liners, and accessory outlet cables. That is, it holds a LOT, and it's totally waterproof, very tough. I'm securing to the bike like an idiot here; it actually secures to the bike with very nice straps. Ortlieb also makes great, tough dry bags.
If you want to have even
tougher luggage, you have to go with a hard luggage option. There are a few options through companies like Norman Hyde (they have a Givi-based rack), but I'm a big fan of my Hepco & Becker setup, which you can buy through newbonneville.com, twistedthrottle.com, and other sites. You can fit any Hepco & Becker standard luggage to the rack, so if my Junior cases look unappealing to you, you could put on
Gobi or
Strayker cases (the Straykers in particular have a nice style, though they are only 23L per case). My cases are totally waterproof and tough as hell. I've been down on the bike three times, with the luggage taking the brunt of the falls. Barely even scratched them, and the frame is still rock solid (okay maybe it's 2mm to the right now, geez).
If you don't have rain gear, you really should get some. It can be a pain in the ass to put on and take off, but when... oh, I don't know, you're riding through tornado weather in Kansas during a torrential downpour and Meade is 150 miles away... you will appreciate it. If you really plan to do a lot of commuting/touring, invest in quality textile touring gear. Many people love Aerostich. I have an Olympia AST jacket with Ranger II pants. The combo works quite well in a nice range of temperatures, though it can be too warm in the summer, even with the liners removed.
As a final option, I would suggest an accessory outlet. The Triumph accessory outlet is pretty inexpensive ($30? I can't remember anymore) but allows you to recharge cell phones/whatever on the road. They take "BMW-style" plugs, which you can find by the truckload at Powerlet's website.
In summary, I would say these are the things you should strongly consider:
* Bar risers/different handlebars (if you need it) - $75 to $100
* Peg lowering kit (if you need it) - ~$50 for modre's
* A different seat (you will almost assuredly need it unless you are a serious iron butt) - $150 to $350+ depending on what you buy and used vs. old
* Some form of wind protection - $90 to $250 (MRA Roadshield to Parabellum LTD)
* Throttle rocker - $10 to $20
* Bar-end weights - $1 for washers to $70 for some nice !!!MANIC Salamanders
Everything else really depends on how nuts you want to go. Hope that helps.