According to the Aufbau Principle, orbitals are filled in the order of increasing energy, determined by the $(n+l)$ rule. Lower $(n+l)$ values indicate lower energy. If $(n+l)$ is equal, the orbital with the lower $n$ value has lower energy.

For the given orbitals:

1. 3s: $n=3, l=0 \Rightarrow n+l = 3$
2. 3p: $n=3, l=1 \Rightarrow n+l = 4$
3. 4s: $n=4, l=0 \Rightarrow n+l = 4$ (Higher energy than 3p because $n$ is higher)
4. 3d: $n=3, l=2 \Rightarrow n+l = 5$

Therefore, the order of increasing energy is 3s < 3p < 4s < 3d. This order governs the electronic configuration of Titanium ($Z=22$): $[Ar] 4s^2 3d^2$, where the 4s orbital fills before the 3d orbital .