D&D Beyond can be used for free and contains information from the following "free to use" sources published by Wizards of the Coast:  D&D 5th edition SRD, D&D 5th edition Basic Rules, and Elemental Evil Companion. The character options you have are available in these sources.

Content from other sources, such as the Player's Handbook, Dungeon Master's Guide, or Monster Manual, will need to be purchased from the Marketplace or accessed via another user sharing content with you via their Master Tier Subscription.

You may also purchase individual races, subclasses, feats & magic items from the marketplace - should you later wish to purchase the sourcebook that they came from, any such individual purchases are fully discounted from the price of the sourcebook.

You are also welcome to create your own content using the D&D Beyond homebrew tools.