The XI is a great starter for you!

As stated, it has a bunch of option parts, and all can be had from TQRC (those that aren't out-of-stock, it IS the popular chassis right now, after all!), which have the lower pricing of many online vendors, domestically. I've also visited their shop/track, and it would surprise you to see just how small the room they do all their parts orders from! It's a hole in the wall!

As for the better parts for the XI, the front one-way is a good start, as is a spool for the rear, and getting many of the main chassis parts that are plastic replaced with carbon or aluminum parts would be adviseable. There is nothing wrong with those plastic parts, but if durability is a concern (or just longevity, since on-road chassis aren't jumped or otherwise abused, unless you insist on running on filthy/rough surfaces consistently), aluminum parts for the main chassis are a good idea. They also make the chassis look purty, which would urge you to treat it better!

Yah, I've been in on-road for some years, and though I'm no expert, I have had a number of chassis (some good, some great, some trash), and am constantly improving them. As a matter of fact, I just made an order with TQRC this morning! I'm currently working on some of my "M" class chassis (just ordered a carbon chassis conversion kit for one), since there isn't a good drift chassis to get, right now. I have two chassis that are my premiere drift chassis to run, and both are VERY similar. The TA06/RSector is one of them, but the TA06 is actually somewhat of a copy of Losi's JRXS Type "R," which is the other one. Both have the center battery mounting/rear-mid-motor arrangement, but unfortunately, the JRXS-R is no longer available.
Really is a shame, since the JRXS-R is F-A-S-T as grip chassis, and near-perfectly balanced, as a drift chassis.

If you get further into drift, and want another chassis (you can't have enough of them, after all! ), I recommend the TA06, since you can't beg, borrow or steal a JRXS-R any longer. You also should, when you get closer to CS'ing, check out a vendor on Ebay called "kaw218." He sells nothing but CS parts for various manufacture RC chassis, and I get my CS stuff from him.