To publicize which night of Chanukah it is, the menorah must easily display how many candles have been lit. Therefore, all 8 candle-holders on the menorah should be at the same height and preferably in a straight line. Otherwise, the candles may not be easily distinguishable and may appear as more like one big torch. Since the Shamash does not count as one of the regular 8 lights, your Menorah should have the Shamash set apart in some way either placed higher than the other candles, or significantly off to the side. The most important thing is that that your candles must burn for at least 30 minutes after nightfall.
Many Jewish bookstores sell longer colored candles.
Actually, it is even better to use olive oil since the miracle of the Maccabees occurred with olive oil. Many Jewish bookstores even sell kits of pre-measured oil portions in disposable cups. These cups can simply be placed in the candle holders of any standard menorah. If this is not practical, then the Menorah should be lit in a window facing the public thoroughfare. Someone who lives on an upper floor should light in a window.