DnD 5e - Intro to Character Optimization
Character optimization is, at its absolute simplest, is the simple act of choosing the better of two or more options when you're building a character.
Character optimization is a lot of what I do on this site. I enjoy it quite a bit, and I love sharing what I know. This page will go into some basic guidance on how to optimize characters, but for specific guidance I encourage you to visit the Character Optimization section of this site.
Understanding a few basic concepts will go a long way to help you build effective characters.
The most important thing you can do for your character is to start with a 16 or 17 in your primary ability score. This is the ability score used for attacks and/or spells. The game expects that you will have a +5 attack bonus at 1st level, and if you don't have that you're behind the game's math. After that, I recommend at least 12 in Constitution, but ideally 14 if you can manage it.
The rules also expect that your primary ability modifier will increase by 1 at 4th level and increase by 1 again at 8th level, which means that the math expects your first two ability scores to go into your primary ability score. If you deviate from this math, try to do so with a really good reason.
Class and Race
Select a class and race that complement each other. This is generally easy to do by selecting a race which provides a bonus to your class's primary ability score.
For example: A high elf wizard is a good class-race combination because the High Elf gets a Intelligence increase. A half-orc wizard is a bad class-race combination because the Half-Orc does not get an intelligence increase, and their other racial traits aren't helpful enough for the Wizard to compensate.
Backgrounds are easy to optimize because there are a lot of published options, and the published rules actively encourage you to make your own by mixing up buts of existing options. Even if you're limited to official options, there are enough backgrounds that you should be able to find a background which complements your character's capabilities. Don't worry about items provided by the background; your class's starting gear is plenty and you'll start collecting treasure soon.
Feats can be confusing, so if you're not ready to explore feats that's perfectly fine. If you want to ease yourself into using feats, stick to feats with simple or passive effects like Skilled or Tough.
Selecting spells is difficult because you have some many options. If you're casting spells offensively, diversity is key: you want a mix of spells which work on attack rolls and spells which target different saving throws so that you can attack enemies where they're weak. For damage spells, try to have a mix of different damage types so that weaknesses and immunities are less of a problem. Remember that you can upcast spells, so even low-level spells can be important offensive options. But don't be afraid to trade out low-level spells if they don't scale well or if you're not using them. Low-level utility options and buffs never stop being useful.
Once you're comfortable with the basics, some more complicated considerations can help you get the most out of your character.
Picking your ability scores at 1st level can be more complicated than just getting a 16 in something. Ideally, you want a general idea of where all of your ability score increases will go and why. If you start with two odd-numbered ability scores, you could put +1 in each at 4th leveland increase two ability modifiers.
For example: Barbarians need high scores in both Strength and Constitution. The Mountain Dwarf provides +2 to both. Starting with a 16 in both scores is great, but if you start with a 17 in both, you can raise both to 18 when you get your first ability score increase at your 4th Barbarian levels. If you don't want to invest so many points in your two most important ability scores, you could instead start with 17 Strength and 15 Constitution, which will still benefit from splitting your ability increase but will let you spend more points on other ability scores.
Class and Race
Your class is more important than your race. Your race is basically a package of traits that should complement your class's capabilities. Ability score increases are probably the most important thing you can get from your race, but consider other benefits as well.
Is Character Optimization Bad?
No. Basic character optimization is not only normal, it's actually expected by the game rules. 5th edition Dungeons and Dragons assumes that you're going to start with at least 16 in your primary ability score. The game expects that your Constitution is going to be higher than 10. The game expects that you're going to design your character to complement the rest of your party. These are all core parts of the game's design, and choosing not to take those basic steps is either a deliberate choice to make the game harder for yourself or a lack of understanding of the game's mechanics.
People who optimize characters go by many names: Min-maxers, munchkins, power gamers, try-hards, etc. These titles are occasionally meant in a derogatory fashion, but those prejudices illustrate a philosophical difference between members of the community. Even people who turn up their nose at character optomization still do it, whether they acknowledge it or not. Even the least mechanically-include players won't walk into a game with a wizard with 8 intelligence except as a joke.