Before you start packing your bag, you should ask yourself these questions:
What is your transportation going to be (bus-train-plane-hitch-walk)?
Where and in which season are you going?
What will you be doing?
Answering these questions will help you to figure out what you REALLY need on your trip. If you are going to travel through northern Europe for 5 months doing many hikes, sure you will need warmer clothes, rain protection and hiking boots. If you are going south to experience hot climate and lie on the beach every day, you will need less jumpers and maybe a swim suit wouldn´t hurt. I´m just recommending.... If really it gets colder than expected, it´s never too late to buy a new jumper which will serve as a nice souvenir, too.
As a general rule, I would say its better to have real, high quality stuff (why does everything have to be cheap or free?) than 2 same cheap pieces of the same. For example it´s much better to have a really warm and good sweater than 2 thin and cheap ones. It will hold for ages and do what it´s designed for: fit and hold warm. Some of these things are highly functional and have a really good style too. Make sure all the clothes match eachother, otherwise you will be quite annoyed.