Any investor who has visited enough finance-related websites will have seen Israeli contract for difference trader Plus 500’s (LSE: PLUS) adverts offering forex, equity and commodity trading amongst others. It turns out quite a few people are clicking these ads and signing up for Plus 500’s services because 2015 saw a 28% increase in new customers. This is one reason shares of Plus 500 have rocketed up in value 44% since the start of the year.

The downside for Plus 500 to these adverts is that they are becoming more expensive as the company targets higher-spending customers. Marketing and sales costs increased a full 67% in 2015, which is why net profits fell 6% over the year. This is a major worry for a CFD trader such as Plus 500 that has sold itself as a growth share and constantly needs to bring in new customers.

Despite shares trading at 8.7 times forward earnings and offering a 7.6% yield, I’ll be avoiding buying a company whose business model is enticing retail investors to bet on the movements of currencies or commodity prices. There are also the regulatory problems Plus 500 ran into last year over not carrying out sufficient due diligence on new customers.

Growth play?

Shares of North Sea oil & gas producer Faroe Petroleum (LSE: FPM) have jumped 28% year-to-date thanks to solid 2015 results. Despite falling crude prices contributing to a 12% decline in revenue, Faroe was able to wring enough efficiencies out of its operations to remain cash neutral throughout 2015 while still spending £62m on exploratory capex.

The generous 78% Norwegian tax rebate that allowed this exploration combined with acquisitions increased 2P reserves by a whopping 88%. With net cash of £68.5m and access to significant credit lines, Faroe has the balance sheet to develop these reserves when the time comes. If Faroe can continue to maintain a healthy balance sheet despite low crude prices while building reserves, the company could be in for good growth once crude and gas prices rebound.

Fickle fashion

The domestic leader in UK online clothing sales, Asos (LSE: ASC) has seen share prices rise 11% so far in 2016 after solid first half results. Year-on-year, Asos saw revenue increase 21% thanks to particularly strong trading in the key EU and US markets. Perhaps even more importantly, gross margins increased a full 50 basis points. This is good news as margins were hit hard in 2015 due to investments in infrastructure and technology.

Shares have an astronomical valuation of 70 times 2016 earnings, meaning the company will have to put in many more quarters of double-digit revenue growth to meet expectations. I also remain leery that Asos can buck the long trend of low-cost, youth-oriented retailers eventually falling out of favour with their core demographic. There are too many examples of the fickleness of 20-somethings’ clothing tastes to make me comfortable investing in such a highly priced company as Asos.

Of course, that doesn't mean growth investors should avoid every retailer they come across. The Motley Fool has detailed one that has grown sales every year since going public in 1997 in its latest free report, A Top Growth Share.

The market has responded well to this success, sending shares up in value nearly 250% over the past five years. And the Motley Fool's crack analysts believe international expansion has opened the potential for shares to triple again in coming years.

To read your free, no obligation copy of this report simply follow this link.

Ian Pierce has no position in any shares mentioned. The Motley Fool UK owns shares of and has recommended ASOS. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.