"Hey Joe", welcome here to our online community.(sorry for the joke)

If you've taken some time to explore the site you'll realise we're a friendly and diverse bunch.

I hope you'll enjoy you time here and that you gain a good understanding of the challenges ahead of you and the best way to overcome them together.

Your first post certainly raises a big ask, and will likely need quite a few inputs to help you with your research.

Before even thinking about the Visit visa please Do not make any travel arrangements/confirmations.

Let's focus firstly on the visit visa.

Securing a tourist visit visa is notoriously problematic for many reasons.
Not least because approval or refusal of General Visitor (tourist) visa applications is principally based on the discretion of the ECO.
Basically there is no appeal process.

The major complication is the need by the applicant to prove a non-immigrant intent. Applicants wishing to come to the UK under a tourist visit must clearly demonstrate that they do not intend to remain in the UK on a permanent basis. Immigration law places this burden of proof on the applicant.
In order to grant a temporary visa, the ECO must be satisfied that the applicant has strong social, economic and family ties abroad that would compel them to leave the UK at the end of the temporary stay.

Unfortunately, in most cases it becomes difficult to overcome this presumption.

The UKBA page specifically for UK Visit Visa's can be found here with additional detailed information which can be found here and also explains what you are allowed to do while you are in the UK as a visitor.
It's well worth taking a look around and checking out all of the links provided.
Anyone coming to the UK as a visitor, will usually be granted a visa with a validity for up to 6 months stay.

Anyone 'sponsoring' a visitor to UK should also review the UKBA webpage Sponsoring a General Visitor

In principle, you must be able to show that:-

- you are 18 or over
- you intend to visit the UK for no more than 6 months
- you intend to leave the UK at the end of your visit
- you have enough money to support and accommodate yourself without working or help from public funds, or you and any dependants will be supported and accommodated by relatives or friends
- you can meet the cost of the return or onward journey
- you are not in transit to a country outside the 'Common Travel Area' (Ireland, the UK, the Isle of Man and the Channel Islands).
- you do not intend to take paid or unpaid employment, produce goods or provide services, including the selling of goods or services directly to members of the public
- you do not intend to do a course of study
- you do not intend to marry or register a civil partnership, or give notice of marriage or civil partnership
- you do not intend to carry out the activities of a business visitor, a sports visitor or an entertainer visitor
- you do not intend to receive private medical treatment

You can downdload the application form and guidance notes from this page

Understand how to apply by reviewing the page Applying for a UK visa in the Philippines

Concerning the actual documents you'll need to submit in evidence, it really does come down to your personal circumstance but generally must contain:-
- information about the applicant
- information about the applicants finances and employment
- the accommodation and travel details
- information about the applicants visit to the UK

As examples of the type of documents that could be supplied Here is the UKBA Guide to Supporting Documents for visiting the UK

For the General Visitor the application should be supported with some of the following documents for a sucessful application:-

- if the applicant is employed, a letter from the employer granting leave of absence from the job for a specified period - the letter should also say how long they have been employed by that employer, in what job(s), and when they are expected back at work
- if they are self-employed, evidence of the business activities and financial standing
- evidence of any property they own in their home country
- if they are a student, a letter from their school or college stating the course they are on, its start and finish dates, and the dates of the holiday period when they intend to visit the United Kingdom
- evidence of any family or social ties and responsibilities to return home to
- evidence of any firm travel plans they have made
- bank statements going back over a period of several months
- evidence of savings/funds available to them during their stay
- evidence that they can financially maintain and accommodate themselves in the UK with or without assistance from family/friends living in the UK but without resource to public funding or employment.

The sponsor can help greatly by providing an invitation/supporting letter to confirm the support they will be providing in terms of financial assistance and/or accommodation.

If the sponsor is intending to totally support the visit this is a listing of fairly typical supporting documents that should be provided:-

- 6 months Bank statements
- 6 months pay slips
- Proff of address (eg utility bill, Council Tax etc)
- Accommodation details (including owner's agreement / rental agreement)
- Sponsors passport copy (Photo page, any relevant stamp pages)
- P60 (if available)
- The main reasons for wanting the applicant to travel at the specific time

The first and foremost thing that you need to keep in mind when applying for a visa for UK, is that there should be an intention to return to the home country.
Have a well thought out travel plan. Date of Travel, duration of stay and reasons for travelling.

The absolute keys are going to be:-

- Reasons to return home that outweigh reasons to stay
- Financials

Reasons to return home and strong/complelling ties differ from country to country, city to city, individual to individual.
Some examples of ties can be a job, a house, social and family relationships, a bank account, possessions etc

The ECO will be looking to see if the aspects of your life that bind you to your country outweigh those aspects that may cause you to be unwilling to return to your home country, or to attempt to change or extend your visa status.

The positive aspect of visit visa application is that of it's very low cost.
So nothing to lose and everything to gain.

On the questions you raise about the longer term, better to wait for while and see how the relationship develops.
Except for Fiance(e)/Spouse/Partner visa etc the only other visa that can lead to a UK settlement visa would be a student visa.Simply because it can be 'switched' to spouse visa.

As a first step in your research/understanding take a review of this thread

In principle the requirements are the same for spouse/partner and Finace(e) visa's

Welcome here and good luck
Don't feel shy to ask questions