Placing different kinds of tikz drawings side by side with captions

Question

Lots of people have approached this question, but none with the twist I think I am suffering from. I am using diagrams both in regular tikzcd and from quiver. I want to place them side by side and to include captions for them. Here is my tex. I get odd errors related to not being in outer par mode, having an undefined control sequence, and missing a number.

Here is the code with some revision:

\begin{minipage}{0.5\textwidth}
\begin{minipage}{0.2\textwidth}
    \begin{figure}
        \begin{tikzcd}
                %\node (point) at (0,0) [circle, fill=yellow, radius=0.3cm] {};
             \draw [fill=black, draw=none] (-0.40,0.25) circle (0.18cm)
                 node (pt1) {};
             \draw [fill=black, draw=none] (0.45, -0.25) circle (0.18cm)
                  node (pt2) {};
         %\node (root) at (0,0) [draw=black, circle, radius=1cm] {};
         \draw [draw=black, ultra thick] (0,0) circle (0.80cm)
             node (planet) {};
         %\node [below = 1cm, align=flush center, text width=5cm]
         %{
            %    A set
         %};
        \end{tikzcd}{\caption{A diagram}}

\end{figure}


\end{minipage}
\begin{minipage}{0.2\textwidth}
\begin{figure}
    \[\begin{tikzcd}
        \bullet \\
        \\
        \bullet && \bullet \\
        \\
        && \bullet
        \arrow[from=3-1, loop left]
        \arrow[from=3-1, to=3-3]
        \arrow[from=5-3, to=1-1,  crossing over]

    \end{tikzcd}\]{\caption{Another figure}}

\end{figure}

\end{minipage}
\end{minipage}{0.5\textwidth}

Let me know how I can improve my question if need be.