Personally, I have experimented with all groups and, besides email list currencies, I can highly recommend any combination. The currencies are, from ATS point of view, highly unstable (for example in Forex, ATS are failing really fast and it is really email list difficult to find profitable ATS for Forex). It also depends on how many markets you create a system for, and how many email list markets you trade with your account. But even with rather a small account, you can trade 3-4 markets.
For such cases, I would recommend email list following combinations: Combination of 3 markets (pick one market from each market group): Index Grains Energies Combination of 4 markets (pick one market from each market group): Index Grains Energies Bonds Nowadays, I trade email list several portfolios that are based on the 4 groups mentioned above. Here is an example of one of them (breakout strategies, 30-minute chart, 5 markets, equity for the last 8 years, trading 1 contract per system).
The net profit for all 8 years and all email list markets combined is 421,548 USD and the max drawdown is just 12,315 USD. Smoothen the equity by using multiple timeframes The second way how to smoothen your equity curve (in a combination of trading several markets from different email list groups) is using several timeframes for every market (ideally without changing system parameters, or with just small changes).