I don't believe in netdecking myself, being victim to several over the years. What I will do however is look up decks that run the same colors I want to run (typically red/black, black/blue or red/blue, although lately I have been experimenting with the new elves from Lorwyn block and mixing them with older classics like Llanowars and the one that allows you to put Llanowar elves tokens in play (from Time Spiral block)) and look at decks for inspiration and put my own twist to them. I have never been to a Magic tournament, but I have played at my local gaming shop. They freaked when I set down at the table and started using Pestilences and other old school cards from before Tempest, as 95% of the guys I played against have never seen cards from before the Urza's block.
I do not buy many new cards (I have not bought a booster box since Onslaught, but I am looking at some of the new precon decks from Lorwyn=present, the black/red one particularly (I think it is Army of Darkness or something)), but when I do, I wait until the initial shock value comes down under $10 (I am still waiting for Twincast, Isochron Scepter, and Panoptic Mirror to come down so I can buy 4 of each for under $10 lol.), and I order them off the internet because I have terrible luck getting what I need from packs.
My most expensive deck cost me around $20. That is because I made a soldier deck using 4x Dariens, 4x Benalish Commanders and 2x Kjeldoran Outposts. The rest of the cards were given to me because they were white and the guy had no use for them lol. I also have a sliver/cleric deck that uses Rotlung Reanimator to regenerate them from the grave lol. That is a fun deck because it uses Mistform slivers so I can change them to clerics, sacrifice them to Cabal Archon, and they come back as zombies thanks to Rotlung. Will either deck win a tournament? Probably not, but they are fun to play and that is all that matters to me. My girlfriend hates both of them lol. She even hates my new elf deck that gains life without using wellwisher. (I told her that if she wants to beat my decks, she should modernize her decks while remaining true to her concept. She just rolls her eyes lol. She still beats me most of the time when we play the WOW card game though (thanks to a semipro giving her tips at a spectral tiger tournament on how to run her warlock deck).