If you want to get any X-game to try it out this is the one (do not play Rebirth first!), it has the least steep learning curve of the series and if you complete the main plot you have a couple million to start trading early rather than grinding back and forth between stations using SETA (you still do that, but not as much).

Combat
The big difference between this and X3:TC is the fact the Argon and Terrans are at war, so there are war sectors included which are interesting and can be dangerous to players, however apart from these sectors the universe feels more safe due to the absence of the Kha'ak. So apart from these sectors and a couple of pirate sectors the universe will feel completely harmless.

The combat is fun (at least in my opinion) as it requires many skills, during your game you will fly smaller fighters in one on one combat, engage against M7 frigates, and finally in Battleship M2 battles, each requiring different tactics to defeat. However the game has balancing issues in some respects, missile frigates can destroy anything, and are frequently spawned from combat missions. Put simply I saw 3 M2's, 2 M1's and pretty much everything else in a sector get destroyed by 1 missile frigate, as the cpu ships don't seem to understand missile defence, the only thing stopping it destroying my fleet was that it ran out of missiles.

Trade

Played an X-game before? Ok skip this part, there is very little change from previous X games in this section as the expansion focuses mostly on combat, except for the inclusion of a stock exchange which allows you to invest in shares, and your actions in the universe affect the share prices based on demand and supply of the good you invested in. Issue being this makes the game very easy if you use exploits or have a complete monopoly within a sector.

For new people the trading is actually quite good at showing simple demand and supply economics (price elasticity may even be present!), put simply buy goods in high supply in low demand in one sector for a low price, next go to a sector where that good is in low supply and high demand. Sell it for profitsssssssss (meet the Teladi) and repeat over and over until you know exactly where the SETA key is.

Exploration

Other than about 2 sectors there is not many new regions to explore from X3:TC, but that does not take away the fact that it is a massive game, and will take you literally days for you to find all of the sectors due to a couple of hidden unknown sectors.

Summary

This game and the X series in general is not for everyone, as it requires the most amount of patience I have encountered in a video game (the many years of Football Manager and Championship Manager are not even close to this for time commitment) but if you stick with it you will uncover a jem of a game, and even if you do not want to spend the time just
install some mods (really recommended for new players as it adds so much to the game), change the players name to "Thereshallbewings" and script in your fleet of Excelsior and Galaxy class ships and the Normandy SR2 as your flagship frigate and take over the Galaxy!