There are 5 tiers of champion rarity, ranging from 1 gold at Tier 1 to 5 gold at Tier 5. At the start of the game, you’ll mostly see tier 1 and 2 champions, but at high levels you’ll start seeing more of the higher tiers. High tier champions are generally stronger than their low tier counterparts, but they’re harder to acquire and upgrade, since they’re rarer and cost more gold. You can sell any unit by dragging them into your shop for a full refund.
While building your composition, keep an eye out for high tier champions available to you. It may be prudent to pivot to a different strategy if you suddenly have access to some high tier units with a different Origin or Class than you originally had in mind. It can also be viable to throw in a Tier 4 or 5 champion that doesn’t perfectly match your team’s Classes & Origins if the champion is strong enough. High tier units that are upgraded are the strongest in the game, so you may want to save some of your items for one of those units.
Rarer units not only have a lower chance of appearing in your shop or the Shared Draft, but there are also fewer of them overall. This makes Tier 5 units difficult to acquire and even more challenging to upgrade. Keep an eye on your opponents’ boards to see what champions they’re picking up to get a sense of how difficult it will be for you to find those same champions. It can even be beneficial to buy a champion you don’t plan on using if it’s a rare and important champion for an enemy’s composition. Use this strategy sparingly though, since you have limited space on your bench.