Mana potions and 100 Mana to chest really aren’t necessary. Though, you shouldn’t be going oom all the time. The only time I ever approach going oom is at the initial fight of an intense game.
What I would recommend is limiting your use of shocks, ie only on Rogues (if not dotted already). 13 mana adds up quickly. Since Healing Surge costs the most mana, you really have to calculate when it’s appropriate to use it and when it’s not. ie predicting who’s going to take a lot of dmg, such as being attacked by a boomkin, having multiple players on them at a given time, etc. Always top off teammates with Riptide. If they aren’t taking much pressure(70% hp ~ +), top them off with a Riptide rather than a Healing Surge. It really just comes down to using your mana efficiently. After a bit you’ll tend to get the hang of it.