Hi Lancaster
Canada has reciprocal arrangements with some European countries for Working Holiday Visa's. Unfortunately Spain is not one of them. The UK, France, Sweden, Austria and many others are, but apart from UK and Ireland you will have a language barrier (unless you can speak French being a Canadian?) to gaining employment.
But if your mates uncle is willing to let you work, it is most likely cash in hand, or work for your board & lodgings. So the less we say on this forum the better.
I do not believe you will be able to get more then a 3 month visa for the Schengen Zone easily or at all. Do not see this as a barrier. See it as a opportunity to visit another part of Europe for 1 - 2 months.
Going to Africa from Asia is a bit of back tracking and then going to Australia will add substantial costs to your airfares.
Use this site to start perusing airfares, www.skyscanner.com . Play around with different locations and you could come up with some bargain airfares. Maybe consider visiting Egypt after Europe, or Turkey on your way to Asia.
Asia is a the biggest continent, with many options. For someone your age I would recommend the tried and tested South East Asia route, consisting of Thailand, Laos, Cambodia and Vietnam. You could also add Myanmar, Malaysia, Singapore and Indonesia into the mix, but not all of them.
Australia is a great place to visit, but is very expensive. Even though I am an Aussie, if you are on a tight budget I would recommend avoiding as you get more bang for $$$'s elsewhere.
Other Asia options that are cheap and easy to get to from Europe are China and India. India is a punch to the face to your cultural senses and probably the most different from Canadian culture. But it can be hard work travelling there.
Budget is dependent on the person. If you want to party all the time it adds significantly to your budget.
Breaking it down though, the travellers main expenditures are food/drink, accommodation and transport. These are what you look to save money on. Catching local buses rather then taxi's or tours. eating at local restaurants or self catering rather at places aimed at tourists. Basic hotels/guesthouses or hostels, then star rated places.
Me personally, for 1 year, I would be wanting to take $25000cad with me. But I enjoy a beer and do not like to work when I travel. A lot of people would of it for a great deal less. India and South East Asia are relatively cheap. Egypt is also. Europe for the most part I would consider expensive for a backpacker and will be the place you will spend the most money apart from Australia.
Seeing you are in Spain you could catch a ferry to Morocco for 1- 2 weeks to give you a taste of something different.
Visa's. Once you have an idea of where you want to go. Use Google to look up the visa requirements of each country as their are to many to through on here when you have not specified a more exact itinerary.
Happy planning