1. What kind of a bike should i be looking for and the cost of it ? geared/non geared/flat bars/etc...
If it was up to me, I would buy what you can afford and personally I would get something with drop bars, gears and room for fenders.
2. What kind of tires do u guys recommend ?
I would recommend something 700c between 28 and 32 width- You don't need to spend a ton. I like Forte Gotham tires for commuting and all-around use.
3. Is buying used a bad idea ?
Buying used is a good idea as long as you know how to appraise the value of a bike and can fix anything you need to fix yourself. Bikes can often be had at a good discount if you buy used- and not a bad idea if you're just getting into biking.
4. What kind of gear should i be looking out for ? Its cold and rainy, very rainy....
I second the idea of using thrift stores. I don't know which are the good ones in Portland, but I know a good one on the west side. Buy Nylon shell pants and upper and then just wear whatever athletic wear you have underneath. Fenders on your bike are a must.