It really depends on your build as to which EB you can hit and which EB is for you but a rough guide is:
- <25 lands with T1 builds stick to Tier 1 Epic Battles
<25 lands with T2 buildings stick to Tier 2 & Tier 3 Epic Battles
<25 lands with T3 buildings stick to Tier 3 & Tier 4 Epic Battles
<25 lands with T4 buildings stick to Tier 4 & Tier 5 Epic Battles
25+ lands with T4 buildings stick to Tier 5 & Tier 6 Epic Battles
30+ lands with T4 & T5 buildings stick to Tier 6 & Tier 7 Epic Battles
40+ lands with T4 & T5 buildings stick to Tier 7 and Tier 8 Epic Battles
50+ lands with T4 & T5 & T6 buildings stick to Tier 10 Epic Battles
Also note: spy builds have a much easier time hitting so Hansels, Hybrids, and Purespies may be able to operate against Epic Battles harder than their Troop Build counterparts.
This guide is by no means 100% accurate and is simply based on my observations.
Some Epic Battles in the same tier are harder than others.
Also, some require different builds to complete.
For example: Foreign Territories is a Spy Only Epic Battle whereas New Growth is practically a Troop Only Epic Battle.
However this guide should give you a basic starting point.