Hello! Don't be afraid, it's really not as hard or as scary as it looks!
Two websites I would really recommend for you, money saving expert (www.moneysavingexpert.com/ ) and Money Advice Service www.moneyadviceservice.org.uk/en - loads of really useful and easy to understand resources on there and MoneySavingExpert also has a great forum with lots of helpful people if you have questions.
I would start by doing a bit of an audit on your finances using one of the budget calculators on the website. These will take you through in a logical way thinking about your finances, starting with income, then essential outgoings on rent, bills, food, commuting costs etc. I would set up your income to come into a current account and then your bills and rent all to come out of the same account, preferably quite close together in the month. The tools will also help you set aside a monthly amount for bills which are less frequent, e.g. insurances which have to be paid annually. It's up to you whether you leave this money sitting in your current account or transfer an amount monthly to savings to cover these bills- when I was first budgeting I would do the latter to make sure I didn't accidentally spend it. Just make sure if you do this it's a relatively easy access savings account and not one where you will be penalised for withdrawing the money when you need to pay the bill.
Then the amount you have left over from your monthly income (after bills and essential expenses have been met) is what you have left for savings and spends! I would set a reasonable, not too stingy amount as 'spending money' for yourself each month - for me this covers clothes, cosmetics, socialising, hobbies, presents for friends/family, some charitable donations and 'fritter' money like coffees out, magazines etc. It's important to have a budget for this so you don't overspend but don't try and deny yourself all treats either as that is unsustainable.
Then what you have left should be for savings. I would use your ISAs for 2 separate savings pots. One should be your long term/rainy day savings pot, not to be touched unless in an emergency or for specific long term goals like moving house. I would want to get to the point where you have 6 months income in this pot before starting on any other savings goals (although driving lessons may be a good investment before then if you need to drive for work).
The second ISA I would use for short and medium term savings, and in this pot I would include things like holidays, a car, new electronics or appliances and perhaps driving lessons depending on how soon you want to take them.
Some people find that a good tip to help them stick to their budget is to withdraw all their food budget/spending money in cash at the start of the week or month and then only ever spend what they have in cash, when it's gone it's gone. Some people keep separate purses for food/groceries and for 'fun' money as well. I have to say this never worked that well for me, I felt the money burning a hole in my pocket and would spend too much when I first made the withdrawal leaving myself short for the end of the month. Plus I felt really nervous carrying around all my cash with me and scared of losing my purse or being robbed. I find it much more convenient to just use debit card for most things and only have a small amount of cash. This has the advantage I can easily track my spending using online banking and can regularly 'audit' where my money is going and target where I can make savings. But I do have to be disciplined and know at all times how much of my monthly budget I have left and not overspend it, it can be easy to lose track when you are just tapping your card on the reader all the time as opposed to handing over cold hard cash. So do whatever suits you best!
Any more questions please do ask and good luck!