You cannot time the market, so SIP is best way.
My suggestion -Please suggest some good Large and Mid cap ELSS MFs.
LARGE CAP
1) MAGNUM TAX GAIN
2) HDFC TAX SAVER
3) BIRLA TAX RELIEF-96
MID/SMALL CAP
1) HDFC LONG TERM ADVANTAGE
2) PRINCIPAL TAX GAIN
3) PRINCIPAL PERSONAL TAX GAIN