Plop the TARDIS down right in your world! There is space inside, so you can add room. Also, you can renovate the control room, and bring in resources to unlock the ability to travel to The End and Nether.

Additional Notes

PLEASE DO NOT BREAK ANY REDSTONE YOU COME ACROSS.

If the teleports don't work, go into creative (if cheats are off, go into LAN mode with cheats on).
and make sure the hopper clocks are synced. So if they are happening at the same time, delay one.

If no commands work, make sure command blocks are on.