Simply play the 1.0 game as it comes, and you will love it. It is a fantastic game, and trying any mods before you've played it through will only ruin the game for you completely.

After you've played it through, I strongly suggest finding an online server and getting out there to play the MP aspect.

After you've done that to death (or if you cannot do that), THEN and ONLY THEN try the mods out. There are plenty of recommendations, and some will immediately say "oh oh oh this one, it's the best". It may be the best, but start small with mods, and work upwards.

Why? Because then you not only prolong the game, but get to appreciate finer aspects of mods, with the ability to "upgrade" to a more comprehensive mod eventually.

After you've got so sick of FL it isn't funny, you then try a total conversion instead.

As Mr Chips says, play it through as is. And don't rush the game. Let Juni hang around in bars and wait for you to show up. You don't have to drop everything and fly back as soon as she calls you. (Tell her you won't do a mission some time and watch her reaction!)

Do some exploring, try different ships, mine, wreck hunt, try different weapons combinations, look for jump holes, find those unlisted bases in unexpected places. Enjoy the fantastic graphics and get as much as you can out of the game. The mods will always be there for later.

For a real challenge, see how far you can get in a low level ship or even in a freighter.

First of all finish the game in Singleplayer, try original Freelancer 1.0 in Multiplayer and then try out mods like Evolution 2.29 NRII or Void2015.
This game is very unique, i play it every day since 3 years now, how he said do not rush and try everything out.