We bought two of the big sets and would still love more of the elevation-changing tracks! You can make some complex tracks with a couple of sets (see video— we didn’t use all the pieces).
My 16-month-old sat on one piece and broke the connector the first time we used it. The track pieces that are connected to risers need to be treated delicately, as the connectors are very easy to break.
The non-track tiles are compatible with most brands’ standard tiles. They aren’t needed for use of this set, but it is always nice to have more building options.
Word of caution — make sure kids with long hair do not get the cars unattended, unless they can be responsible to keep them away from their hair! We had both daughters get their hair stuck in the wheels!