Buying a combination gauge is more cost effective as it essentially combines the marking and mortise gauge into one gauge. Paul recommends the type that have pins rather than discs as the discs tend to be brittle and fracture in places around the circumference. Discs are often difficult to re-sharpen and if broken can be impossible. Some gauges come with wear plates in the stock part of the gauge. Depending on the atmosphere/humidity, these wear plates can protrude above the wooden surface of the wood and this can affect the accuracy of your marking.
Amtech is a less expensive choice than Marples and works just as well. You can also buy secondhand as they can be cheaper, for example Clay or Mawhood are both good Gauges which Paul has bought secondhand. No matter if you are buying new or used, make sure to check that the pins are in good condition and are of equal length before you buy.
We purchased this Silverline Expert Combination Gauge from Amazon for £15.34 in November 2017.
If you are ordering from the US, we recommend this one. Please note Paul has not purchased this, however it seems to fit his recommended criteria.