UT not recommended unless u really have no idea on how to invest your money.
UT fees & commissions will be there irrespective of the funds performance.
Up or down the UT fund managers are making money out of u.

If u still want to buy then look for low cost UT, typically index type fund
or better still put your money in index linked ETF.

Invest periodically. When price is high u get less units and when low u get more units. In the long run your cost will average. (dollar cost averaging).
So this will eliminate the timing issue.

Money used for this investment should be for long term saving. (Retirement,children's education fund etc.) Not money you are going to use next year or so.