Start off slowly, and with quarter notes. Those would be easy to keep up with as you progress your speed
Then eighth notes. Start slowly, then build up. If you're just working on timing, don't move around the fretboard to begin with. Keep with one or two notes (alternating, of course)
Sixteenth notes could come after, but they play just like eighth notes, just faster.
Triplets may come in handy too, but keep those for last.
Once you have all of those, alternate between the quarter, eighth, and sixteenth in each measure. Use patterns like: quarter, eighth-sixteenth-sixteenth, sixteenth-sixteenth-eighth, eighth-eighth (should be four beats total).
Then start with dotted notes. Dotted quarter, eighth, eighth, dotted quarter.
This is how I learned. And remember: PRACTICE PRACTICE PRACTICE. Practice as much as you can.