Railroad ties are fairly inexpensive and fairly easy to use. Their disadvantages include that they are somewhat temporary (the probably won't be in great shape after a decade or so) and they could be (depends on various factors) dangerous to use for a vegetable garden. Properly installed landscape block (especially the 16" and larger ones) make an excellent material, but they are expensive and a little more technically difficult to install. Lumber may work OK for smaller beds, but it will probably need to be replaced on a somewhat regular basis (especially if it's not treated, which is what you'd probably want if you're growing food).

They type of soil you need will depend almost entirely upon what you plan to grow! If you are doing a rock-garden, you'll need a very sharply draining medium (probably mostly rock and sand). If you are growing things that require decent drainage, you'll need to provide good drainage, and building soil structure (with a certain percentage of organic material) will be important. If drainage doesn't matter, then you choices will be greater.

We just built raised beds from used pallets. It's free wood, your repurposing it, and it hasn't been treated with any chemicals so it works well for edibles. We don't expect our beds to last forever, so no disappointment there!