Using "Level Up!" on "Silent Magician LV4" is a much quicker way to Summon "Silent Magician LV8" than using its own effect. A good combo is using "Shining Angel", "Arnis, the Empowered Warrior" or "Magician's Circle" to Special Summon "Silent Magician LV4" to the field, then using "Level Up!".
Combine this card with "Secret Village of the Spellcasters". Since it is a Spellcaster, the opponent won't be able to activate any Spell Cards, and once it has five Spell Counters on it, it will have ATK equal to "Silent Magician LV8".
This card works great with "Defender, the Magical Knight" as the Spell Counters on it will supply its defensive effect and when the opponent draws a new card it will regain Spell Counters.
This card works well with "Tempest Magician" as it can add most of the Spell Counters instantly, or if it has five Spell Counters on it already, your opponent can be dealt an instant 2500 damage, then replenish them.
In a Deck with "Magical Citadel of Endymion", it might actually be more beneficial to not Level this card up. If this card gains 5 counters and is destroyed with "Magical Citadel of Endymion" on the field, "Endymion, the Master Magician" could be easily Special Summon when the Spell Counters are saved by the Field Spell.
This card is useful in a Deck that abuses the effect of "Greed". Allow the opponent to draw outside of the Draw Phase; not only will the opponent be damaged at the end of the turn, this card will get loaded with counters and its ATK will increase. "Level Modulation" can also be used to recover this card (or its more powerful form) from the Graveyard.
Equipping this card with "Unstable Evolution" is incredibly practical; with Life Points lower than the opponent's it will gain and additional 1000 ATK (for a max of 4900 ATK with 5 Counters), but with higher Life Points, the original ATK of "Silent Magician" simply goes back to normal.