It can be slow getting started, and there's really no way to make TU really fast, it just takes patience.
In addition to selling creatu, you can also invest in stocks. Buy low, sell high, and you can never lose. This also takes patience, but has a much larger payout over time as you accumulate more shares. Right now, SWE is a good one to buy, it's at 34 TU per share, and you can purchase up to 50,000 shares of it. If you are able to purchase it, don't sell it until it is over 300 per share, or even over 400 per share. You'll make a very hefty profit. =)
To use the creatu search properly to see prices, make sure you set the Location to Rancher Shops, then choose the Species you are wanting to price, then the Color. Under Display options, use the CTRL key to click and select Owner, Name, Species, Color, Price, and Location if they are not already selected. These are the columns that will display in your search results. Next, set the minimum Price to 1, and leave the maximum Price blank. Under Order By, choose Price. Choose Ascending to see the results from lowest to highest, Descending to see the results from highest to lowest.