I only have experience coming from 3e/4e. My only advice is to look at things from a fresh approach, and don't read restrictions that aren't there.
5e is very intentionally an exceptions-based rules design. There's very little to no hidden subsystems that require knowledge of other subsystems in order to properly use player abilities. Things normally happen as per the basic rules, as presented in the Basic Rules, as a player handout in LMoP, or in the SRD. Class abilities, including spells, count as exceptions to those rules, and are self-contained. To quote a phrase popular in another WotC game, Magic the Gathering: "Reading the card explains the card." Rather than glancing at an ability or spell and guessing what it does or how it interacts with something, just actually read the very short paragraph explaining what it does. For mechanical effects, this wording is chosen very deliberately. You can always make exceptions if you want, but exceptions made deliberately to enhance the game are much better than exceptions made accidentally that might unbalance the game.
If anyone plays a spellcaster, make sure they have access to full descriptions of what their spells do. If they say they want to cast a spell, ask what it does, and if they say they don't know, then *someone* look it up and read its entry out loud in full. It will explain if the effect just happens, requires an attack roll, or saving throw. It'll explain how far away the effect is, and how big it is, whether it affects a single target, multiple, everyone in an area, or if you can exclude people. It'll explain how long the effect lasts, if it's just instantaneous, or sticks around for a while, and whether the spellcaster has to maintain concentration to keep it going.
This includes monster stats. Don't accidentally give monsters resistance or vulnerability to damage that they don't have. 5e zombies, or example, don't take extra damage from holy sources (unless that ability says it does), nor do they take reduced damage from bludgeoning weapons, and a rogue's Sneak Attack damage can apply to them. Again, you can make exceptions if you want to make a custom zombie that's particularly vulnerable to (or resistant to!) Sacred Flame, but knowing what's baseline and rules-as-written I believe can make you better informed to make those exceptions in a way to enhance your game.