Difficult to answer that question without some idea of what you want to shoot. Or some idea of what you want to spend. There are a lot of choices, both in the Pentax line and in third party offerings.
You have two very good primes in your Takumars. Get the adapter, preferably the authentic Pentax one, although some of the cheaper ones work also. Be careful to NOT get one with a flange as you will not be able to focus to infinity with them. You might check out the sticky
here before you use them, it will save you some time getting them to work. Also the Takumars have a strong following
here you might be interested in.
For a general purpose lens, not too expensive, that fills out your line up you might look at the Pentax DA f/4-5.8 55-300mm. It is a solid, reliable performer with good range. It also comes in a DA L version which is a bit cheaper but lacks quick shift and the hood. Tamron has an offering in this range as well.
In the Pentax-A line up the f/1.4 and f/1.7 50mm turn up regularly and are highly regarded. You can also usually find the f/2.8 28mm. Other than those, A-series lenses are somewhat rare and a little expensive.