I have been thinking about trying to get into the ultima series and i am wondering if i need to play the games in order or if there are some i should skip. i am also wondering if i should try the one you get for free or if that would ruin the previous games.

I'd start with Ultima 4, since it's really where the story about The Avatar starts.

Yeah, Ultima 4 is the best place to go. It's especially useful because of the rapid pace at which the games improve as you play them.

My suggestions are release order, though skip the Ultima 6 side series (Martian Dreams and Savage Empire) if you don't feel like playing Ultima 6 anymore, because they are essentially Ultima 6.

1. Ultima 4
2. Ultima 5
3. Ultima 6
*Savage Empire
*Martian Dreams
4. Ultima Underworld
5. Ultima 7
6. Ultima Underworld 2
7. Ultima 7 Part 2

Then stop. Turn back. There is nothing good beyond this point, despite some maybe speaking to a contrary. This is three purchases in total and every bit as worth it as anything. Make sure to download the GoG resources and use the forum resources!

I tried playing the games in the order they were made, but the first trilogy has aged quite a lot. There is a clear lack of balance and quite a lot of grinding. Play them only if you are curious.

Ultima IV, Underworld, VI and VII are god starting points, but each one has some barrier of entry.

Ultima IV is the oldest one on the list, so it is the one with the most antiquated interface and graphics. It fixed the balancing and grinding problems of the first trilogy for the most part and it is also the point when Ultima began taking its definite shape. it was where the virtues got introduced and it was where the land of Brittania got defined. Before each game has its own geography, but now the geography would say mostly the same and evolve.

Ultima VI is a good starting point because its more modern engine, interactive world (you can pick up and move objects) and it introduces the gargoyle race. The biggest problem is its interface, the game is more advanced than the interface could handle. Fortunately there is an open source port called Nuvie, it features a fullscreen interface mode similar to Ultima VII. Nuvie is still in development, but it should be good enough to play through the game (projects like this tend to get stuck in eternal beta due to perfectionism, even though they work well enough)
http://nuvie.sourceforge.net

Ultima VII is considered the best game in the series, but it is also the largest of the games. It is very easy for newcomers to simply drown in all the content. I guess it depends on what one considers to be the "best". Similar to Ultima VI there is a port for this one as well, it's called Exult:
http://exult.sourceforge.net
The download says unstable, but ignore that, it works well. Remember, eternal beta...

Ultima Underworld is another great entry, very modern design and surprisingly good interface (read the manual about "default mode"). the only problem is that it's not really an Ultiam game. It's a great introduction to the universe though. When I got fed up of the first trilogy I played though Underworld before going to Ultima IV and I loved it.

I also think Ultima IV is a good starting point for a new player.

The thing about the first three is that, not only are they much more primitive, but the story they tell sort of stands on its own. You'll find references to it in the later games, but you can safely leave it for later without any ill effects on the narrative.

That said, I still quite like the first three, although that's partly nostalgia.

it's difficult to imagine what would be most appropriate for a pre-Ultima consciousness, since i was 11yo when introduced to III and 13 when IV came out. V was the first PC software purchase i ever made, for my glorious 8088 XT with 640k RAM and an amber monitor... before long i was sneaking it into the academic computing center at [innocent university redacted] for the full color and the not-wanting-to-gnaw-your-foot-off pace...

i think it primarily depends on how much 'history lesson' you can stomach as a player. for me the innovation of IV's morality system was crucially formative both personally and... gamer-ally?

and though the 'watch the plot/interface/etc. improve by leaps and bounds' isn't quite compelling enough for me [...yet...] to go back to III (or even start I or II), partially because i know there won't be any ~Virtue~ involved (i do miss customizing a party, larks and thieves, and even, sometimes, endlessly pillaging Yew... but not quite enough to go back, yet.)...

i'll assume that not quite wanting to go back to the most primitive origins (yeah yeah, you see what i did there) is the 'norm', dismiss the first trilogy (*sniff*)...

and call it a toss-up between IV and V for a solid 'grounding'. i suppose V -> VI is the most satisfying 'upgrade' experience, but that of IV -> V, compounded with the first (of two consecutive) character transfer mechanisms, will always bring me, personally, back to the original Quest of the Avatar.

with all the love i have for III, IV, V, VII and IX, i still don't count as a True Fan because (a) i've never gone back to I and II (though i did look at Akalabeth for a few seconds once) and (b) i chickened out on UO because i suspected (with copious supporting evidence) that i would allow it to consume my life. (of course later, when i found out friends were making a comfortable-if-temporary living selling off characters, felt extra-stupid...)

I have to agree with everyone else, that IV is the ideal starting point for someone who is just starting their journies through Brittania for reasons already listed above. But I'll also add that Ultima III isn't bad either if you download the Ultima Patcher program and put the EGA patch on it, which gives it music, new tileset, and EGA graphics. I recommend reading up about the plot (little that it is) of the first 2 games, and giving III a try, and then if you just can't stomach that one either, even after patching it, then start at IV like everyone else has suggested.