I need to buy some new clothes for the summer.

to buy some new clothes to buy is asking what new clothes. I am saying an adverb again

1. What is the WHOLE infinitive phrase?

2. Re-think what this phrase is doing. Re-read the five examples of infinitive phrases I already gave you. Also study this: "Adverbs can be single words, or they can be phrases or clauses. Adverbs answer one of these four questions: How? When? Where? and Why?"
http://www.chompchomp.com/terms/adverb.htm

Let me know what you decide.

to buy some new clothes

to buy what some new clothes A noun

Whole infinitive phrase:

to buy some new clothes for the summer

The main clause is "I need" -- and the infinitive phrase is serving as a noun, the direct object of "need." See the second example here:
http://grammar.ccc.commnet.edu/grammar/phrases.htm#infinitive

write down the details in the seating of "how much land does a man need ?"

To buy some new clothes for the summer, there are a few steps you can follow:

1. Assess your current wardrobe: Take a look at what clothes you currently have and determine what items you need to add for the summer. Consider the weather, your personal style, and any specific occasions you may have during the season.

2. Set a budget: Determine how much you are willing to spend on your new clothes. This will help you prioritize your purchases and ensure that you don't overspend.

3. Research and create a shopping list: Look for inspiration online, in fashion magazines, or even on social media to get an idea of the styles and trends you like. Once you have a clear vision for your summer wardrobe, make a shopping list of the specific items you need, such as dresses, shorts, t-shirts, or bathing suits.

4. Choose your shopping method: Decide whether you prefer shopping in physical stores or online. Each option has its advantages, so consider factors like convenience, variety, and the ability to try clothes on before purchasing.

5. Start shopping: If you prefer shopping in physical stores, look for local malls, boutiques, or department stores that carry the type of clothes you are looking for. It can be helpful to call ahead to ensure they have the items in stock. If you prefer online shopping, visit reputable websites or apps that offer a wide range of summer clothing options.

6. Try on and evaluate: When trying on new clothes, make sure they fit well, are comfortable, and make you feel confident. Consider factors such as fabric quality, durability, and versatility to ensure your new clothes will last throughout the summer season.

7. Make the purchase: Once you are satisfied with the items you have chosen, proceed with the purchase. If shopping online, follow the website's checkout process, providing payment and shipping information. If shopping in-store, head to the checkout counter to complete your transaction.

Remember, always double-check the store's return policy in case you need to exchange or return any items that don't meet your expectations.