Multiclassing with spell slots is a great way to increase your ability to cast spells. By taking levels in a class that has access to spell slots, you can add new spells to your repertoire.
This can be a great way to customize your character and make him or her more powerful.
However, multiclassing with spell slots comes with some caveats. First, you must be able to cast the spell from the class you are multiclassing into. Secondly, if you take levels in more than one class that has access to spell slots, the total number of spell slots you have available for casting spells is divided among those classes according to their level requirements.
For example, if you are a Level 5 druid and want to take levels in an arcanist class that grants 4 additional spell slots, you would have 2 additional spell slots (1 from the druid level and 1 from the arcanist level). If you wanted to take levels in two classes that grant 3 additional spell slots each, you would only have 1 additional slot (since both classes require Level 4 characters to take them).