Re: Legend of the Five Rings, CCG
For starters, poke around on the L5R mainsite til you find their forums. You can also try hitting the clan forums for the Spider. These will give you insight into deck strategy.
If you know the specific cards you want, there's two ways to go about getting them. First, you can buy the expansions the cards come from and hope to get lucky. You MIGHT get by more cheaply this way if you're lucky or have trading partners, but the more cost effective method for single clan players (like yourself) tends to be hitting up the secondary market. eBay, Roku-Mart, or L5rsearch can get you what you're looking for, and the latter two are sortable based on legality and clan.
On legality: to identify whether a given card is Emperor (that's the current arc) legal, you should look for the Emperor edition kanji symbol in the lower left corner of the text box. It's green. Any card with that 'bug' printed on it is legal in the current arc, though if you've got older printings of the card, those work too. As far as what sets are currently legal:
Before the Dawn
The Second City
Forgotten Legacy (a direct to player set only accessible by ordering from AEG)
The Shadow's Embrace (a factory set, again only accessible from AEG)
Embers of War
Seeds of Decay
specific cards from War of Honor (a big box usually in the board game section)
For competitive play, you'll want Forgotten Legacy (currently available for $75 as a just the cards deal), and The Shadow's Embrace along with singles from the secondary retailers. FL gets you the experienced starting holdings as well as power unique strategies like A Game of Dice and Creating Order. TSE is also a solid set and both have strong in clan cards. TSE pricing gets a bit hairy, I think you can pick up just the strategy pack and your clan pack for around $160 or so. That gets you your clan's personalities and all of the miscellaneous cards that fit in multiple clans.
Keep an eye out for the upcoming Gempukku edition. It's rumored to be an awesome set that gives lots of rares for cheap. It may be a worthwhile investment, but it's too early to tell.
Welcome to the game!