What kind of bike should I ride?/clothing to wear?
Do not spend a significant amount of money on a fancy new bike until you are sure cycling is for you. As long as your bicycle is comfortable for you and the tyres and brakes are in good condition then it will probably be fine for the purpose, at least in the early stages. Even so there are 3 items that we would highly recommend:

1) Try to avoid carrying rucksacks. A rucksack can be heavy and uncomfortable. If your bike cannot readily take a saddlebag then take it to your local bike shop to have a carrier fitted. This is easily done and will enable a saddle bag to be used for carrying your essentials.
2) Mudguards. We won't insist on these on your first ride but they are extremely useful to prevent both you and your cycling companions from road spray and dirt should it rain, or even if the roads are wet from another source. In the long run we will ask that mudguards are fitted for everybody's benefit.
3) Helmets. There is no legal obligation for a helmet to be worn. The CTC's advice is that the case has not been properly made and in some cases the use of a helmet could be misguided. In practice about half the active Essex DA membership wear helmets with the others deciding against. It's all a question of personal preference.