I would suggest serching out a club local to you. Make friends and ask questions. Im sure you will find, like all clubs, that they are more than willing to help with your initial setup/choices and intoduction to flight. Also dont rule out the used market for equipment, often times you can find an older setup in the classifieds for an excellent price. When it comes to a transmitter make a choices based on the type of flying you plan on doing in the future not what your doing now. If you plan to get more complicated setups than invest in a good computer radio with model memory and mixing fuctions. If you only plan on doing light sport flying than a cheaper radio with fewer options will suffice and the money saved can be spent elswhere.
When it comes to servos, buy the ones most suitable to the application. Your model should have suggestions as to what servos best fit the needs, make your choice around those requirements. As far as batteries go again dont over buy, choose those that fit thr requirements of the application, again your model should have suggestions. Remember money not wasted is money to spend elswhere.

In the case of a Sig Kadet Mark II I would suggest four basic servos, nothing special is required, 35 to 40 in/oz is sufficiant. The JR 517 comes to mind. You should only need one servo extension for the ailerons all the others should plug directly into the receiver.

For a battery I would suggest at least a 700mah pack. I would also suggest starting with a nicd pack as these are more forgiving and lend themselves to some one who is learning the hobby in that they are harder to ruin through charging practices.