As a GM, there is one thing I hate that new players do above all other things:
Don't Be Afraid To Ask Questions Or Speak Up
One of the things that new players do a lot is... nothing. They don't feel comfortable yet, so they don't say a lot. That's to be expected, and it's okay.
But then you get the ones who won't ask questions when they're confused, won't speak up when they have an idea, and won't let anyone know that they're bored and not having fun.
Don't do that. If you're confused by a rule, how a spell works, or if you can use an ability to spy on an NPC, ask. Ask every question you can think of. I'll happily spend half the night answering questions that help you get into the game. I want you to be able to do things, and am much happier answering questions that help you do that than I am if you just sit quietly because you're confused or unsure what to do.
If you have an idea for the party, speak up. Maybe it's not a good idea. Maybe it's an obviously genius idea that they never thought of because they've been in the game too long. Who knows until you voice it? The entire point of the game is to interact with the other players, so please do it when you have something to say.
And of course, if you don't feel like you can do anything and aren't enjoying yourself, I want to know that! There's lots of things the GM can do to help you out, if you tell us. But we're not mind readers, and we really don't like finding out later that you're unhappy when we could have done something about it had you said so earlier. (This can be done by passing a note or asking to talk in private, if it's something you don't want to voice in front of the group.)
Group Specific Stuff
Beyond that, it's a hard question to answer. Group dynamics and expectations vary wildly between groups. In some groups, you should wait your turn to speak and do things politely. In other groups, you're just expected to interrupt when you have something to say, and not doing so is treated as quiet agreement.
Some groups are quiet, others get very animated. Some expect people to only talk in character, others are assumed out of character. Some groups will do a lot of talking and try to solve mysteries or deal with things peacefully, and others shoot first and maybe ask questions after the loot is counted.
There's numerous examples of things like that, and as I know nothing about your group, I can't really say what they expect you to do. Except that they want you to ask questions and get involved. :)
Unless Warcraft changed something, mundane crafting does not cost XP
Mundane crafting requires Craft skill checks, but no Item Creation feats, and the costs are only time and money, not XP. Specifically, they cost a mere ⅓ of the base price of the item, but crafting takes a number of weeks equal to
(P×10)/(DC×check)
where P is the item's usual price in gold pieces, DC is the Craft DC, and check is the crafter's Craft check result. This formula results in phenomenally long times, but at ⅓ the cost there is a lot of savings.
Magic items require XP, but that is easily replaced
In many places, XP costs are replaced with gp costs or vice versa at a 1:5 ratio. Since magic items cost 50% the base cost in raw materials and 4% the base cost in XP, you can apply the same conversion: five times the 4% is 20%, which can be added on to the existing raw material cost to get 70%.
Thus if magic items simply cost 70% of the base price to craft, instead of 50%, but don't require XP, this is consistent with the original system. Taking an Item Creation feat only enables a 30% discount but doesn't leave you behind.
I have played in quite a few games that make this change; it didn't dramatically improve the popularity of Item Creation feats for players, but it does make them much less of a headache for the DM.
If playing with Eberron Campaign Setting (the book, regardless of whether you play in Eberron) in play, the artificer and Artisan feats do require a little more tracking: it is important to remember that 50% of the base price is the original raw material gp cost, while 20% is the "XP" cost. The artificer's Craft Reserve and Retain Essence class features, as well as the Artisan feats, should be applied before adding these together as the 70%. The Craft Reserve should also be multiplied by 5 gp/XP for consistency.
If either is too expensive, these items were not intended for characters of their level
These processes both result in significant discounts. The value of items is used to control the power of items that players have at a particular level, which is part of the system used to try to ensure that enemies the same level as the players are challenging without being impossible. Making items cheaper or giving players more gold may allow them to steamroll opponents; making items more expensive or giving players less gold, or giving them gold but no place to spend it, may leave players without the tools they need to contribute.
In my experience, there are many classes that just barely find the default wealth rules sufficient for their needs – if they spend carefully. Other, more powerful classes are not nearly so needy, and could do with less. As a result, reducing wealth is something I strongly recommend against – it disproportionately hurts the classes that were already weakest.
On the other hand, I tend to find the system has a fair amount of room for extra wealth before players really start to steamroll. Thus, your choice to make it easier to get items is a move in the better direction.
But do be careful; wealth expectations are a rather fundamental design assumption of the game. Great care should be taken when modifying it. I tend to recommend that new DMs stock fairly close to the guidelines. It takes experienced DMsa lot of care to get modifications to wealth to work the way they want.
Best Answer
Ideally? You don't need to buy anything at all.
You should ask your GM ahead of time if there's anything they specifically want you to bring, but here is the important thing to remember about the books, or any gaming kit really:
It can and should all be shared by players and GM alike
I can think of very few items in a gaming system that cannot be borrowed from another person or easily produced for free. Dice can be lent (most experienced players will have a collection anyway), books can be borrowed (as a beginner, you may want someone else to help you make your character anyway), and character sheets can be printed off the web or simply fabricated with paper and pencil/pen. The Game Master is usually the one responsible for bringing books to a gaming session, so unless you plan on being the Game Master right away (not recommended—experience playing is the best way to learn good game master practice), you can count on the game master for your gaming tools.
Now don't feel like if you've bought a few 3.5e books already that you need to return those books right away. It's easier to make your own character as you see fit when you've got your own copy of the rules. But, don't feel like you must have any particular book to play a game either—a good Game Master will provide for new players, and good players will help new players along.