By 30 mos, 20 teeth
The central incisors come first: bottom (mandibular) before top (maxillary) for 4 total by about 8mos.
Then lateral incisors-4 (8-9mo), canines-4(16mo), first molars 4 and second molars-4 for a total of 20. This is the typical order, but I have seen high variability in this sequence. By 2, usually 16 teeth have erupted, and sometimes all 20. My twins had no teeth until 12mos old!