What sort of holiday do you want? A package holiday somewhere in the sun? That might be the easiest route in. I tend to book my own trips, flights, hotels etc but it might be easiest to book a package holiday with Tui or Jet2 as others have said. It is VERY IMPORTANT you book these directly and don't try to save a bit of money by booking via a 3rd party. British Airways also offer holidays that generally are the same price as just the flights. Check your passport has more than 6 months left in it at the time of your trip - before you book (this caught me out once).
Where: I'd recommend you stay in Europe. I love the Greek islands for sun, nice food, beautiful sea. I love Crete. Avoid Zakynthos. You don't need to go to the famous places to have a lovely time - you pay a premium for them.
When researching, check out reviews on Google from people who have stayed there and their photos of their stay, look at photos on Google Maps, check what the local beaches actually look like, are there huge motorways close by etc. Do you want self-catering or a hotel? I'd recommend avoiding the huge AI resorts and go for somewhere smaller, e.g. that has its own pool and the beach is short walk away. I like to go for a place that offers breakfast, get a snack at the beach for lunch and go out for dinner. But have a think about what your ideal holiday would look like - what do you do each day? Do you want to be able to visit places or just chill? Be in the middle of nowhere or near a little town for walking around in the evening? Do you want to go out for cocktails and dancing every night, or drink wine on your room's balcony before a quiet dinner and an early night? This will help you work out what you want and are willing to pay for.
A package tour will get you from the airport to your hotel - but make sure there are as many amenities nearby as you need within walking distance (e.g. supermarket, restaurants - it may be none if you're going for a resort).
When you book the holiday, get checked luggage as particularly the budget airlines are MEAN about the rules and it's just a stress. Check not only the dimensions of your baggage but also weight (some places like Ryanair require luggage under 10kg which is bonkers). You can buy cheap suitcases on Amazon. If you check luggage you can also take suncream with you - the stuff from Aldi is great.
Buy travel insurance as soon as or even before you book your holiday. Moneysupermarket for comparisons, but Admiral and the Post Office offer good products. Often an annual multi-trip isn't much more than an individual trip and covers you for overnight stays in the UK.
I take about £100 in local currency, as I have a debit card and multiple credit cards I take with me, and most places take cards these days. Take a smaller purse with just your debit cards, credit cards, GHIC card and driving licence - but your loyalty cards all stay at home. If you want to be super covered, take pictures /photocopies of all your cards and your passport, keep them in the hotel safe in case they get lost / stolen (in 27 years of international travelling I've never had anything stolen).
If you are travelling in Europe apply for the GHIC card which covers you for medical treatment post-Brexit. https://www.nhs.uk/using-the-nhs/healthcare-abroad/apply-for-a-free-uk-global-health-insurance-card-ghic/
Take 2 swimsuits, and fewer clothes than you think. Don't take expensive jewelry on holiday. Take a sarong and one of these in XL https://uk.dockandbay.com/?tw_source=google&tw_adid=0&tw_source=google&tw_adid=0&nbt=nb%3Aadwords%3Ax%3A20048024048%3A%3A&nb_adtype=&nb_kwd=&nb_ti=&nb_mi=&nb_pc=&nb_pi=&nb_ppi=&nb_placement=&nb_li_ms=&nb_lp_ms=&nb_fii=&nb_ap=&nb_mt=&gad_source=1&gclid=Cj0KCQiAtOmsBhCnARIsAGPa5yaqZHdkoRROctT5zlkUUEWzlvuUa6OmnxWDQUnItj70F4Cl3Vaj4CYaAmpKEALw_wcB
At least one pair of trainers for walking around.
Wear comfortable things on the plane. Small bag with toiletries of no more than 100ml each. Only take what you need on the plane - lip balm and hand cream. I always take 1 swimsuit in my hand luggage just in case my suitcase is delayed (never happened to me). Use your beach bag as your hand luggage (check airline restrictions for hand luggage). You'll only need minimal make up on holiday, and don't take fullsize toiletries - you can buy minis at Boots before you go or silicone bottles to decant your faves.
Make sure you have enough of any medications several weeks before you travel. Carry those in your hand luggage. Take a reusable water bottle, empty, through security and fill up on the other side. Use your card for a small purchase at the airport and your bank will realise you are going on holiday.
Apologies for the essay!