First, what is your budget?
I use a Nest gimbal head on a Nest Tripod. They are carbon fiber and therefore lighter than some others.
MT Shooter here on the UHH is the US distributor for the heads as he was involved in their design (the US head is not the same as the international model you see on Amazon and Ebay).

https://www.cameracottage.com/apps/webstore/

You can get a head and medium weight tripod (MT refers to it as a light weight but it has a 44# weight rating-Nest NT-6324CT CF Tripod) for just about $600 plus tax and shipping. The head is fluid dampened and in two versions, the second being an Arctic model for cold weather or those who don't like the stiffness of the heavier dampening on the standard model).
I bought my head from MT Shooter and got my tripod second hand

First, what is your budget?
I use a Nest gimbal head on a Nest Tripod. They are carbon fiber and therefore lighter than some others.
MT Shooter here on the UHH is the US distributor for the heads as he was involved in their design (the US head is not the same as the international model you see on Amazon and Ebay).

https://www.cameracottage.com/apps/webstore/

You can get a head and medium weight tripod (MT refers to it as a light weight but it has a 44# weight rating-Nest NT-6324CT CF Tripod) for just about $600 plus tax and shipping. The head is fluid dampened and in two versions, the second being an Arctic model for cold weather or those who don't like the stiffness of the heavier dampening on the standard model).
I bought my head from MT Shooter and got my tripod second hand

I took this first image earlier this morning with a 150-600 Sigma Sport @460mm and a D810, hand held.

But I took the second picture with the same camera and lens, @600mm, but at 1/25 sec also hand held. The third image is the full image that the second one was cropped from.

Are you sure you need a tripod and gimbal?

You may want to try shooting without a tripod - in the case of the cat picture - it was a feral cat - and had I set up the tripod and gimbal and put the camera on it, the cat would have been long gone, and you wouldn't be looking at the "grab" shot I posted. You'll be surprised at how effective the optical stabilization is on the current lenses. I certainly was. I have had this lens 2 1/2 yrs, and have taken 6,000 pictures, and have yet to use a tripod with it. You might call it my wildlife "walkaround" lens.

I also have a 600mm F4 which, together with the camera and battery pack, weighs nearly 14 lbs - it is not possible to hand hold that thing.

If you decide to get a tripod - the minimal tripod I would get would be one that has a top leg tube diameter of 37mm or bigger. Gitzo Series 4, Leofoto LN364C, RRS Versa 3, Feisol CT3372 or 3472, or comparable - will be the correct tripod. The least costly would be the Leofoto and the Feisol, both are under $600. As far as a gimbal is concerned, I use a simple Manfrotto 393 - which is indestructible - and I paid $180 for it.

If you don't want to invest the $$, then don't. Save your money - getting an inadequate tripod would be a terrible waste of good money for you. You always need to make decisions like tripods for the worst case scenario - which would be a 600mm lens, which will vibrate on an unstable tripod - anything less than the Leofoto or the Feisol falls into that category. Just because you only use your Tamron occasionally does not diminish the need for stability. If you use it once a year, you'll still need the stability. If you use it 5x a week, then I would consider an RRS tripod - expensive but there is a great company that stands behind it's products and has exceptionally good customer service. I can personally speak about Feisol's customer service - which is also very good on the two occasions I have used them in the past 12 yrs with my CT3472.

BTW, my diminutive friend - a 66 yr old woman, 4'11" and 100 lbs - uses her Tamron G2 150-600 and a D800 hand held as well - she doesn't own a tripod. And she gets exceptional results.