As detailed above there are so many possibilities to explore. From those you have specifically mentioned I have been to Gambia (going again in November), Goa and Texas (going again next April).
Gambia is just 6hours flight away and in the same time zone and with some terrific sub-saharan species plus a few commoner species from Europe. Small sized country and with birds everywhere. Goa is also easy to do with equally amazing birding within close proximity of the hotels.
Texas is excellent in spring, especially April into early May, with a visit to the Upper coast at High Island for 2 weeks providing super opportunities for american warblers and tanagers at their best.
Spain will be a lot closer and have a more familiar UK feel to some of the birdlife with added bonus of some species which occur in the UK as rarities (Rollers, Bee-eaters, Bustards, Great Spotted Cuckoos etc) plus species which would be specialities to the area, Extramadura would be a great choice.
Personal favourite of mine is Israel in spring (multiple trips in the past decade), usually lots of migration going on in March through to early May with skies full of Raptors and Storks, deserts with its specialities, parks with exotics, salt pans with waders and flamingo's and so on, and its only 5hours flight to Tel Aviv.
All of these places you can do yourself and don't have to go on an organised tour which means you dictate how long you stay where and with what birds and not tied to moving on with the group.
Cloudbirders is the go to place for Trip Reports with many providing very detailed information.
Once you start birding overseas it'll be hard to stop wanting to do more