This is a difficult question to answer not knowing the specific product, the effect you want, what you are treating or your tolerance. I am not a doctor so this represents my own experience and opinion.
First, your tincture has 3 parts CBD to 1 part THC. CBD mitigates the effect of THC, meaning it takes the edge off the high. This would most likely qualify as a 'borderline' psychoactive product. That said, you take enough you will get high as a kite.
Ratios can be misleading because unless you know the milligrams of CBD to THC you could ingest a little or a lot of THC depending on the labeling and what the product suggests as a dose. My suggestion is that you start with no more than 2.5mg of THC and see how you feel before you proceed. 2.5mg is a microdose and you may feel no effect. You can then try 2.5mg more. That would put you at 5mg. 5mg is enough to make someone fell altered. That said, this is general guidance just to keep you safe.
I use a product that is higher CBD to THC and the dose I take typically is 2mg of THC and I do not feel it. The effect I feel is slight relaxation but it seems to work as I don't get regular migraines, so it seems the overall effect is a longer term relief from pain that does not show up anymore. Everyone is unique.
Tinctures usually take anywhere from 10-30 minutes to take effect. Proceed with caution, start 'low and slow' and you can always add more.
Hope this helps and again, it is general guidance.