Praise be to Allah.
With regard to dealing in used clothing that comes from Western countries, the matter is subject to further discussion:
If it is being sold without being sorted or finding out what a consignment contains, it is not permissible to buy it, because that comes under the heading of ambiguity, which is forbidden because of the report narrated by Muslim (1513) from Abu Hurayrah who said: The Messenger of Allah (blessings and peace of Allah be upon him) forbade transactions involving ambiguity.
These clothes are usually sold in large, sealed containers or bags, so it is not known what they contain; they may contain items of low or high quality, things that are good and things that are not good. This unknown factor renders the transaction invalid, because one of the conditions of a sale being valid is that it be known what is being sold, either by seeing it oneself or by having it described, and that is not the case here.
If these clothes are sold after it is known what they are, and the buyer is no longer unaware of what they are, then in principle it is permissible to buy them, unless they are haraam, such as clothing that is only worn by the disbelievers, such as the yarmulke (skullcap) worn by the Jews, or clothing on which there are crosses or images that are venerated. See the answers to questions no. 221847, 112052, 10439.
If clothing from disbelievers is washed, there is nothing wrong with using it, according to scholarly consensus. Rather the difference of opinion is as to whether it is to be regarded as pure or impure before washing. The most correct view is that it is permissible to use that which is not known to be impure, because the basic principle is that things are pure.
However it is better and more appropriate to wash them before wearing them, so as to avoid going against the view of those scholars who said that it is obligatory to do that, and as a health precaution.
See: al-Mughni by Ibn Qudaamah (1/97) and al-Mawsoo‘ah al-Fiqhiyyah (40/105).
With regard to shoes that are made from animal leather, the matter is subject to further detail, as explained previously in the answer to question no. 143663.
And Allah knows best.