DO NOT level 3* heroes before or at the same time as 4* ones. Level 4* first. (Assuming they are the same color, and even if different colors, leveling 4* first is usually the better choice but that’s situational)
4star 3/60 >>>> 3 star 3/50 (maxed)
4star 4/70 (maxed) > 5 star 3/70
The reason is because the gulf between 3* and 4* is so vast where as 4* and 5* have a much smaller gap. New players should always, ALWAYS level 4* before 3* AND 5* heroes regardless of what ascension mats they have/expect to have.
There is no “practical” value to suggesting that new players should level 3* before 4*. The rare stage in events that only allows 3* heroes is a time and effort trap. You get no unfarmable ascension mat, not one, from finishing the rare difficulty monthly events and only delay your progression toward important goals (lvl 4* to complete rare quests, epic+legendary events, better titan scores etc).
There are certainly uses for rare heroes in wars, events, titan stacking etc. There are players who beat the dark lord with 3* or get top 10 scores on rare event and get a mountain of goodies, but none of these points have anything to do with new players. New players do not have the knowledge or experience or ability to use 3* heroes to “punch above their weight” so to speak.
Obviously if 3* is all you got then use what you got. But by far, the most bone headed advice I ever got was to level 3* heroes when I had 4* available just so I can do/finish rare challenges, which I did quite easily no less. And it was the most bone headed decision I made in this game listening to this advice, from my first alliance leader no less.
Edit: Didn’t mean to sound so harsh, but I guess I felt pretty steamed. I don’t believe above posters mean any harm, but this is imho, the worst advice that gets frequently passed around without any thought. Just because maxed 4* beats unascended 5* doesn’t mean maxed 3* beats unascended 4*.
Now if the rare difficulty events actually offered something usable…then maybe we can discuss but no point in any discussion at this time.