Guys you know the 4th slot in your inventory?
It has something called a trinket.
When you click on it, it places a ward at your specified location and grants you vision of its surroundings.
Use it! It's free!
It also recharges for free, so you don't have to cheap out on them.
There's also things called control wards, they cost 75 gold and they can be stacked up to 2 and only one can be placed at a time by every person.
They give you mostly the same benefit of vision but they have a massive advantage - they allow you to disable your enemy's wards and destroy them ensuring the enemy don't have vision on that bush. That's why they are called *control* wards, they let you control the vision in the area.
They don't decay and are visible to enemies, though. You should use them, they are extremely powerful.
Vision is power! Take advantage of it!