By far the easiest way to rank up into gold was to get basic lvl 1 summoners with specific use scenarios. Whoever tells you to buy up summoners beyond lvl 1 is unnecessarily wasting your money. I have one level 5 summoner for my legendaries, but realistically I never use him because the lvl 1 summoners are just too powerful when mixed with certain cards.
I believe Chaos legion is an excellent opportunity to pick up summoners for cheap and have excellent utility for tournaments and the chaos rank battles. But I am certain you only need to venture above lvl 1 summoners past gold 1 and into diamond league. Even gold 1 I am very competitive with my minimal decks.